Zou Chenglu (1923-2006) is a native of Qingdao, Shandong Province. He was a biochemist. He graduated from Chemistry Department, National Southwest Associated University in Kunming in 1945, and received Ph. D. in biochemistry of the University of Cambridge, England in 1951. He was a pioneer of biochemical research in China and a world-renowned scientist of Institute of Biophysics, Chinese Academy of Sciences. He was elected as an academician of CAS in 1980 and of the Third World Academy of Sciences in 1992. He served on the 5th to 8th National committee of the Chinese People's Political Consultative Conference, the national top advisory body, and also its 8th standing committee.

Zou was among the first to use partial proteolysis to study the structure-function relation of proteins. He showed that succinate dehydrogenase is not identical to cytochrome b as believed by many authors at that time. He was among the first to purify this enzyme and showed that it has covalently linked FAD as the prosthetic group. He successfully obtained insulin from the reduced A and B chains by oxidation. This paved the way for the total synthesis of bovine insulin which was awarded National Natural Science Award, First Class in 1981. He treated the effect of chemical modification of proteins quantitatively and proposed a graphical method for the determination of the number of essential residues in 1962. The equations obtained are known as Tsou equation and the plot as the Tsou plot. He pioneered the study on irreversible modification kinetics of enzyme activity and showed that the concept of substrate-inhibitor competition applies to both reversible and irreversible cases. He was awarded National Natural Science Award, First Class in 1981 and again in 1987. He was awarded the Prize in Life Sciences of the Third World Academy of Sciences in 1993 for his contribution to enzyme inhibition kinetics. He had won National Natural Science Award, First Class twice and CAS Natural Sciences Award, First Class for four times.

RELATIONSHIP BETWEEN MODIFICATION OF FUNCTIONAL GROUPS OF PROTEINS AND THEIR BIOLOGICAL ACTIVITIES

C.L. Tsou

(Institute of Biophysics, Chinese Academy of Sciences)

Abstract

The relationship between structure and function of proteins is an important field of study in biochemistry and chemical modification of proteins has been extensively used for the purpose of ascertaining the amino acid residues which are essential for the activities of proteins, especially enzymes, so as to provide crucial information on the possible mechanism of action of the proteins concerned. However, the quantitative relation between the extents of modification of the side chain functional groups of the amino acid residues in the proteins and their inactivation had not been duly considered by earlier workers in this field. A kinetic treatment was proposed by Koshland and Ray in 1961 to establish such a relationship. Although this treatment was an important breakthrough it was limited in its application in that the reaction had to follow the first order kinetics and at a rate amenable to analysis by conventional methods. In 1962, C.L. Tsou made an entirely different approach in the treatment of the quantitative relation between the extents of modification of the side chain functional groups and the inactivation of proteins statistically. Based on the above treatment, a method was proposed for the determination of the number of essential residues among those modified by suitable plots, now known as Tsou plot. As it is not required in this method to follow the course of the reaction and the reaction kinetics can be of any order, this method is of general application and can be used in almost any case. The principle underlying this method has since been further explored and shown to be theoretically sound by a number of authors both in China and in other countries. The method has since been widely used in the world literature for ascertaining the number and kind of essential groups in proteins by chemical modification methods. The details of this method can now be found in textbooks on enzymes, enzyme kinetics and chemical modification of proteins.