AWARDEE OF LIFE SCIENCES PRIZE

XU GENJUN

Abstract

Xu GenJun，research professor, biochemist, was born in Shexian, Anhui Province. He graduated from Chemistry Department, Fudan University in 1957. Since then he has been working in the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences. He was elected the academician of the Chinese Academy of Sciences in 1991. he was elected  vice president, in 1997, and president, in 2001, of Chinese Society of Biochemistry and Molecular Biology
In 1950s he joined the project of total chemical synthesis of bovine insulin, He reduced the disulfide bonds of insulin with sodium liquid ammonia and removed all protected groups including benzyl derivatives in the synthetic A- and B-chains of insulin in sodium-ammonia system and recovered its biological activity by reoxidation after reduction of the A- and B-chains.
In 1960s he studied the kinetics of enzymes and chemical modification of proteins. He extended the conclusion of Morales and Botts and indicated that the Michaelis constant should equal to its equilibrium constant for a system involving two catalytical intermediates if a typical non-competitive inhibition existed, For protein chemical modification, he pointed out that the essential disulfide bridge for trypsin was two not three, as reported by Liener, and supported the correctness of the equation for calculation of essential groups in proteins proposed by professor Tsou Chen-lu.
In the end of 1960s to the early 1970s, when the genetic engineering had not been established, he proposed and developed an approach to study the relationship between the structure and function of proteins by using native peptide and succeeded in the insulin studies. He purified snake muscle fuctose-1,6-bisphosphatase, determined its sequence, cloned and expressed the enzyme and determined the crystal structure, discovered that a phosphoryl intermediate was involved  in the catalysis of snake muscle fructose-1,6-bisphosphatase and the molecular basis of signal transmission from the allosteric site to the catalytic site, found the dual regulated function of AMP for the enzyme, suggested the imperfection of the catalytic site in native regulatory enzymes, and defined the catalytic and allosteric sites of fructose bisphosphatase of rabbit liver before the 3-D structure of the enzyme being determined. In the study of chicken liver fructose-6-phosphate-2- kinase/fructose-2,6-bisphosphatase, he defined that the catalysis of kinase was ordered Bi Bi mechanism and the regulation function of Mg2+ for both kinase and bisphosphatase. He also discovered that a nonessential residue with pKa 9.2 could improve the efficiency of enzyme catalysis, and demonstrated that thymosin β-4 is synthesized in macrophage rather than in thymus cell.
Recently, he has been studying on the folding and refolding of proteins, particular on the folding of the nacent peptide chains and the formation and destruction of domains during the unfolding and refolding processes and obtained some important results.