Contains research objectives.National Institutes of Health (Grant GM-07803

Hammes, G. G.

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XI. MECHANISM OF ENZYMATIC REACTIONS'Prof. G. G. Hammes Dr. H. O. Spivey J. E. ErmanDr. T. C. French T. B. LewisRESEARCH OBJECTIVESIn recent years, considerable effort has been expended in the elucidation of biochem-ical mechanisms utilizing physical chemical techniques. This project, while still makinguse of general physical chemical techniques, is primarily concerned with kinetic studiesof chemical reactions of biochemical interest. A number of techniques have recentlybeen developed which permit the study of chemical reactions with half-times as short-10 1as 5 X 10 sec. The advantage of being able to carry out kinetic studies over anextended time range is that the entire course of a chemical reaction can be observed.Since reaction intermediates are directly detected, detailed chemical mechanisms canbe obtained.The work that is being done can be roughly divided into two classes: the study ofmodel systems, and the study of biological systems themselves. By studying relativelysimple model systems, complex biological processes can be better understood. In thisconnection, studies of the interaction of metal ions with amino acids, peptides, phos-phates, and polymers have been carried out 2 in an effort to understand the role of metalions in enzymatic catalysis. Since macromolecules are necessary for almost all bio-logical processes, chemical relaxation processes of simple polymers, polypeptides,proteins, and polynucleotides are being examined, particularly with regard to the possi-bility of fast conformational changes. "Stacking" interactions of small molecules(e. g. , acridine orange) with macromolecules are also being investigated.In addition to model systems, several enzymatic systems are being studied. Resultsare already available in two cases, aspartic aminotransferase and ribonuclease.3' 4Some detailed information about the nature and number of reaction intermediates hasbeen obtained. As a result, considerable insight into the elementary steps in enzymemechanisms has been gained. Since the structural determination of macromolecules isnow feasible, it should ultimately be possible to understand enzymatic mechanisms on amolecular basis.G. G. HammesReferences1. G. G. Hammes, Quarterly Progress Report No. 65, Research Laboratory ofElectronics, M.I.T. , April 15, 1962, pp. 5-6.2. G. G. Hammes and J. I. Steinfeld, J. Am. Chem. Soc. 84, 4639 (1962).3. G. G. Hammes and P. Fasella, J. Am. Chem. Soc. 84, 4644 (1962).4. Renata E. Cathou and G. G. Hammes, J. Am. Chem. Soc. 86, 3240 (1964).*This project is supported in part by the National Institutes of Health (GrantGM-07803).QPR No. 76

Mechanism of Enzymatic Reactions

Contains research objectives.National Institutes of Health (Grant RG-7803

XI. MECHANISM OF ENZYMATIC REACTIONSProf. G. G. HammesJ. E. ErmanT. B. LewisRESEARCH OBJECTIVES AND SUMMARY OF RESEARCHIn recent years, considerable effort has been expended in the elucidation of biochem-ical mechanisms utilizing physical chemical techniques. This project, while still makinguse of general physical chemical techniques, is primarily concerned with kinetic studiesof chemical reactions of biochemical interest. A number of techniques have been devel-oped recently which permit the study of chemical reactions with half times as short-10 1as 5 X 10 sec. The advantage of being able to carry out kinetic studies over anextended time range is that the entire course of a chemical reaction can be observed.Since reaction intermediates are directly detected, detailed chemical mechanisms canbe obtained.The work that is being done can be divided roughly into two catagories: the study ofmodel systems, and the study of biological systems themselves. By studying relativelysimple model systems, complex biological processes can be better understood. In thisconnection, studies of the interaction of metal ions with amino acids, peptides, phos-phates, and polymers have been carried out2 in an effort to understand the role of metalions in enzymatic catalysis. Since macromolecules are necessary for almost all bio-logical processes, chemical relaxation processes of simple polymers, polypeptides,proteins and polynucleotides are being examined, particularly with regard to the possi-bility of fast conformational changes.In addition to model systems, several enzymatic systems are being studied. Results3,4are already available in two cases, aspartic amino transferase and ribonuclease.Some detailed information about the nature and number of reaction intermediates hasbeen obtained. As a result, considerable insight into the elementary steps in enzymemechanisms has been gained. Since the structure determination of macromolecules isnow feasible, it should be possible ultimately to understand enzymatic mechanisms ona molecular basis.G. G. HammesReferences1. G. G. Hammes, Quarterly Progress Report No. 65, Research Laboratory ofElectronics, M.I.T., April 15, 1962, p. 5.2. G. G. Hammes and J. I. Steinfeld, J. Am. Chem. Soc. 84, 4639 (1962).3. G. G. Hammes and P. Fasella, J. Am. Chem. Soc. 84, 4644 (1962).4. R. Cathou and G. G. Hammes (in preparation).This research is supported in part by the National Institutes of Health (GrantRG-7803).QPR No. 72

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Mechanism of Enzymatic Reactions

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