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MOSES KUNITZ
December ~ 9, ~ SS 7—April 20, ~ 9 78
BY ROGER M. HERRIOTT
MOSES KUNITZ iS best remembered for his isolation and
crystallization of a half-dozen enzymes and precursors.
This work tract two important effects. First, the variety of the
enzymes he isolated and the clarity of his evidence that the
enzymes were proteins convinced those who tract reservect
judgment on the earlier reports of Sumner, Northrop, Cald-
well, et al. Second, his reports of the crystallization of ribo-
nuclease and clesoxyribonuclease, which appeared just as the
functions of nucleic acids were beginning to be explored,
proviclec! information on the high specificity of these en-
zymes. This information made them valuable tools for other
researchers in their purification or the assignment of a bio-
logical function to either RNA or DNA, the two types of
nucleic acid. -
Moses Kunitz was born on December 19, 1887, in SIon~m,
Russia, where he was educated before emigrating to the
Uniter! States. In 1909, he took up residence in New York
City. Entering the Cooper Union School of Chemistry in
1910, he gracluatec! with a bachelor of science degree in
1916. In the fall of that year, he enterer! the Electrical Engi-
neering School of Cooper Union, where he studied until
1919 when he transferred to the Columbia University School
of Mines Engineering anti Chemistry. In 1922 he marricu-
305
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306
BIOGRAPHICAL MEMOIRS
later! as a graduate student in Columbia's Faculty of Pure
Science, which awarded him a Ph.D. degree in biological
chemistry in 1924.
Kunitz derived much of his formal education in graduate
science from evening classes he attendee! while working full
time as a technical assistant in Jacques Loeb's general physi-
ology laboratory at the Rockefeller Institute for Medical Re-
search. Loeb quickly recognized Kunitz's fine work habits ancT
encourages! his educational development. When Kunitz re-
ceived his doctorate, Loeb secured his appointment to the
staff. He also colIaboratec] with Kunitz in studies of protein-
ion equilibria and related phenomena, and many of the orig-
inal measurements on this subject appear in Kunitz's cloctoral
thesis ant! early publications.
Upon Loeb's death in 1924, John H. Northrop was ap-
pointed his successor. He invited Kunitz to continue with his
fundamental studies of viscosity, swelling, and the effect of
certain salts on the properties of proteins. Northrop joiner!
Kunitz in many of these investigations a happy, productive
collaboration that was to last for more than thirty years.
Northrop and Kunitz mover! to the Princeton branch of
the Rockefeller Institute in 1926, and soon after the move,
their interest shifted to the isolation of proteases. Northrop's
choice of pepsin and Kunitz's choice of trypsin for these stucI-
ies were due in part to the commercial availability of these
substances. Although crystals of trypsin were obtained in
1931, the procedure was long and teclious, and the yielcl was
low. In 1933 Kunitz devised a better approach. Preliminary
experiments revealed that unlike the common structural tis-
sue components, trypsinogen, the precursor of trypsin in
beef pancreas, was soluble and stable in cold, quarter-normal,
sulfuric acid. This information led him to clevelop a unique
method of extracting trypsinogen and several other precur-
sors ant} enzymes.
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MOSES KUNITZ
307
Variations of the fractions in Kunitz's assays soon revealed
the presence of another protease precursor and enzyme. Be-
cause the new protease had strong milk-clotting action (a
property not held by trypsin), Kunitz termed the precursor
chymotrypsinogen and the enzyme chymotrypsin. In a rela-
tively short time, Kunitz crystallized both chymotrypsinogen
ant! trypsinogen and, soon after, the active enzymes them-
seIves. Solubility studies that Northrop anc! he had cleveloped
shower! these four proteins to be homogeneous. Kunitz also
found conversion of trypsinogen to trypsin to be autocata-
lytic—that is, tryspin catalyzed the conversion. Trypsin also
converted chymotrypsinogen to chymotrypsin, the kinetics in
this case being first order.
Kunitz's extreme care in all of his experiments frequently
led him to discoveries that the average worker might well
have missed. Two instances illustrate this point. Kunitz inves-
tigatec3 a slow change in the activity of a stores! preparation
of chymotrypsin that he believed to be stable. In the course
of the work, he isolated two new autolysis products, still pro-
teolytically active, which he named beta and gamma chymo-
trypsins, designating the original enzyme alpha. Again, when
his trypsinogen preparation became active in acid solution-
a result contrary to his earlier studies—he discovered that his
stock HC! solution was contaminates! with a mold that liber-
atect a protease that hac! brought about the activation. He
isolatecl the mold an(1 then the mol(1 protease. He then used
the protease to convert trypsinogen to trypsin in an acid me-
dium, obtaining a cleaner preparation of trypsin than was
possible by any previous procedure.
The presence of substances inhibitory to trypsin in the
original pancreatic extracts, and in certain soybean meal frac-
tions, led Kunitz to the crystallization of a polypeptide inhib-
itor from the pancreas and a protein inhibitor from soybean.
Isolation of the inhibitor from the pancreas answered a.ques-
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BIOGRAPHICAL MEMOIRS
tion Kunitz had already posed: Why does trypsinogen re-
main inactive in pancreatic tissue when the pH is optimal for
· · ·
its activations
Kunitz's interests, however, were far broader than merely
the isolation of enzymes or inhibitors. In each instance, he
studied the interaction of the inhibitor with the enzyme and
isolated the complexes, studying their stoichiometry and
other properties. One of his finest papers details the study
of the kinetics and thermodynamics of the reversible dena-
turation of the soybean trypsin inhibitor.
From 1939 to 1940, Kunitz worked to isolate ribonuclease
from beef pancreas. He found it to be one of the smallest
proteins and extremely stable even to boiling. This enzyme
liberates only pyrimidine mononucleotides from ribonucleic
acids. The isolation of desoxyribonuclease came ten years
later, after Maclyn McCarty had obtained its partial purifi-
cation. Very low (nanogram) levels of this enzyme destroyed
the pneumococcal transforming activity of Avery, MacLeod,
and McCarty's DNA preparations a finding that led many
investigators to believe that DNA carried hereditary deter-
minants.
With the onset of World War Il. when the laboratory's
attention was focused on government projects, Kunitz was
asked to isolate hexokinase, thought to be highly sensitive to
the action of a poison gas. He isolated the hexokinase in crys-
talline form, but had to isolate three other crystalline proteins
before the hexokinase crystallized.
The following anecdote reveals Kunitz's remarkable fac-
ulty for crystallizing proteins. Another laboratory had de-
voted considerable effort to the isolation of a plant protein
of great interest to the Department of Defense, but the in-
vestigator had been unable to crystallize the protein. A pack-
age of the material was sent to Kunitz with the request that
he attempt to crystallize it. The package arrived late one
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MOSES KUNITZ
309
afternoon. Kunitz ctissolvec! some of the cIry powder in water
anc! placed small aliquots in a series of test tubes to which he
acl(lecl drops of ctilute HCI, increasing the number of drops
in each successive tube. A precipitate soon began to appear
in the micIdIe of the series, ant! Kunitz hell! a turbid tube to
the light from the window, remarking, after a few moments,
"It looks granular." He placer! the tubes in the refrigerator,
and the next morning several tubes had crystals of what
proved to be the active protein.
It is unfortunate that more beginning investigators clid
not get the chance to work near Kunitz in the early years.
Margaret McDonald and this author were certainly enricher!
by our long association with him. After his return to New
York in 1952 and the conversion of the Rockefeller Institute
to its present university status, Kunitz was named professor
emeritus and continued to work claily in the laboratory. Many
staff and students then tract an opportunity to see how the
master workocI.
Kunitz's papers, moclels of scientific reporting, also illus-
trate his reliance on the results of broad experimentation
rather than on preconceived notions. His procedures of ex-
posing proteins to strong acid or high temperatures unique
at that time were avoided by most investigators.
There is no more appropriate testimony to the esteem in
which Kunitz was held by his peers than the comments of
John Northrop, which were included in a review of Kunitz's
work when he was awarded the Car} Neuberg Medal in 1957:
"Dr. Kunitz possesses to a rare degree the abilities of a re-
search worker of the first rank in his chosen field imagi-
nation, ingenuity, persistence, great technical skill, mathe-
matical facility, and a thorough theoretical knowledge. It is
not surprising, therefore, that he has been able to solve al-
most every problem he has attempted. Some of them are of
great importance. The isolation and crystallization of ribo-
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310
BIOGRAPHICAL MEMOIRS
nuclease, hexokinase, and deoxyribonuclease placed the pro-
tein nature of enzymes, in general, on a firm experimental
foundation. In addition, the nucleases have been invaluable
tools in the elucidation of the chemistry of the nucleic acids,
those remarkable substances that appear to be the very 'stuff
of life'."
Moses Kunitz was a modest, gentle, considerate person
who loved his work and his family. His association with the
Rockefeller Laboratories spanned a period of fifty-seven
years. He died April 20, 197S, in Philadelphia, Pennsylvania.
He is survives! by a daughter, Roslyn Albert, and a son,
Jacques Kunitz.
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MOSES KUNITZ
311
HONORS AND DISTINCTIONS
Moses Kunitz was associated with The Rockefeller University for
almost sixty years (1913-1972~. He was elected associate member
in 1940, member in 1949, and professor emeritus in 1953. Kunitz
was awarded the American Society of European Chemists and
Pharmacists (New York City) Carl Neuberg Medal in 1957. He was
elected to the National Academy of Sciences in 1967 and received
an honorary degree from The Rockefeller University in 1973. He
was a member of the American Association for the Advancement
of Science, the Society for Experimental Biology, the American So-
ciety of Biological Chemists, and the Society of General Physiolo-
gists.
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312
BIOGRAPHICAL MEMOIRS
SELECTED BIBLIOGRAPHY
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With I. Loeb. Valency rule and alleged Hofmeister series in the
colloidal behavior of proteins. I. The action of acids. l. Gen.
Physiol., 5:665 -91.
With l. Loeb. Valency rule and alleged Hofmeister series in the
colloidal behavior of proteins. II. The influence of salts. l. Gen.
Physiol., 5:693-707.
1924
A cell for the measurement of cataphoresis of ultramicroscopic
particles. l. Gen. Physiol., 6:413-16.
With J. Loeb. The ultimate units in protein solutions and the
changes which accompany the process of solution of proteins.
I. Gen. Physiol., 6:479-500.
Valency rule and alleged Hofmeister series in the colloidal behavior
of proteins. III. The influence of salts on osmotic pressure,
membrane potentials, and swelling of sodium gelatinate. J. Gen.
Physiol., 6:547-64.
With I. H. Northrop. The combination of salts and proteins. I. I.
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1925
With I. H. Northrop. An improved type of microscopic electroca-
taphoresis. I. Gen. Physiol., 7:729-30.
1926
With I. H. Northrop. The swelling and osmotic pressure of gelatin
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With I. H. Northrop. The combination of salts and proteins. II. A
method for the determination of the concentration of com-
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Physiol., 9:351-60.
An empirical formula for the relation between viscosity of solution
and volume of solute. J. Gen. Physiol., 9:715-25.
With J. H. Northrop. The swelling pressure of gelatin and the
mechanism of swelling in water and neutral salt solutions. J.
Gen. Physiol., 10: 161-77.
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MOSES KUNITZ
1927
313
Hydration of gelatin in solution. I. Gen. Physiol., 10:811.
With I. H. Northrop. The swelling of isoelectric gelatin in water.
II. Kinetics. I. Gen. Physiol., 10:905 - 26.
1928
With J. H. Northrop. Preparation of electrolyte-free gelatin. J.
Gen. Physiol., 11:477-79.
With }. H. Northrop. Combination of salts and proteins. III. The
combination of Curly, MgCl2, CaCl2, AlCl3, LaCl3, KC1, AgNO3,
and Na2SO4 with gelatin. I. Gen. Physiol., 11:481-93.
With H. S. Simms. Dialysis with stirring. I. Gen. Physiol., 11:641-
44.
Syneresis and swelling of gelatin. I. Gen. Physiol., 12: 289-312.
1929
With I. H. Northrop. Fractionation of gelatin. I. Gen. Physiol.,
12:379-90.
With I. H. Northrop. The swelling of gelatin and the volume of
surrounding solution. I. Gen. Physiol., 12:537-42.
1930
Elasticity, double refraction, and swelling of isoelectric gelatin. I
Gen. Physiol., 13:565-606.
With I. H. Northrop. Solubility curves of mixtures and solid solu-
tions. I. Gen. Physiol., 13:781-91.
1931
With i. H. Northrop. Swelling and hydration of gelatin. I. Phys.
Chem., 35: 162-84.
With I. H. Northrop. Isolation of protein crystals possessing tryptic
activity. Science, 73:262-63.
1932
With J. H. Northrop. Crystalline trypsin. I. Isolation and tests of
purity. J. Gen. Physiol., 16:267-94.
\Vith J. H. Northrop. Crystalline trypsin. II. General properties. J.
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With J. H. Northrop. Crystalline trypsin. III. Experimental pro-
OCR for page 314
314
BIOGRAPHICAL MEMOIRS
cedure and methods of measuring activity. I. Gen. Physiol.,
16:313-21.
1933
With J. H. Northrop. Isolation and properties of crystalline tryp-
sin. Ergeb. Enzymforsch., 2: 104 - 17.
With I. H. Northrop. Isolation of a crystalline protein from pan-
creas and its conversion into a new crystalline proteolytic en-
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With I. H. Northrop. Uber die Wirkung des kristallisierten Trypsin
auf Penta-glycyl-glycin, trim alanyl-~ alanin und Tetra-dl-alanyl
dl-alanin. Fermentforschung, 13 :597-600.
1934
With M. L. Anson and l. H. Northrop. Molecular weight, molecu-
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With l. H. Northrop. Inactivation of crystalline trypsin. l. Gen.
Physiol., 17:591-615.
With l. H. Northrop. Autocatalytic activation of trypsinogen in the
presence of concentrated ammonium or magnesium sulfate.
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With I. H. Northrop. The isolation of crystalline trypsinogen and
its conversion into crystalline trypsin. Science, 80:505-6.
1935
With J. H. Northrop. Crystalline chymotrypsin and chymotrypsi-
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new proteolytic enzyme and its precursor. I. Gen. Physiol.,
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A method for determining the rennet activity of chymo-trypsin. }.
Gen. Physiol., 18:459-66.
With H. Hotter and I. H. Northrop. Spaltung von Clupean durch
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1936
With J. H. Northrop. Pepsin, trypsin, chymo-trypsin. In: Handbuch
der biologischen Arbeitsmethoden, ed. E. Abderhalden, pp. 2213-
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MOSES KUNITZ
315
Handbuch der biologischen Arbeitsmethoden, ed. E. Abderhalden,
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1938
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Formation of trypsin from trypsinogen by an enzyme produced by
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Formation of new crystalline enzymes from chymotrypsin. Isola-
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With J. H. Northrop. Solubility curves of pure proteins and of mix-
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1939
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Formation of trypsin from crystalline trypsinogen by means of en-
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Purification and concentration of enterokinase. I. Gen. Physiol.,
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Isolation from beef pancreas of a crystalline protein possessing
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1940
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1941
With M. R. McDonald. The effect of calcium and other ions on the
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BIOGRAPHICAL MEMOIRS
vol. 2, ed. E. Bamann and K. Myrback, pp. 1940-41. Leipzig:
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1945
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1946
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1947
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Isolation of crystalline desoxyribonuclease from beef pancreas.
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MOSES KUNITZ
1950
317
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1951
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1952
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1953
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1960
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1961
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Representative terms from entire chapter:
trypsin inhibitor
