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Biomedical subjects

T E Barman

Publications and source records attributed to T E Barman.

30 records · Page 2Linked to original sources
PubMed1966

Optical and chemical identification of kinetic steps in trypsin- and chymotrypsin-catalysed reactions.

Previous interpretations of the mechanism of trypsin- and chymotrypsin-catalysed reactions in terms of two intermediates, the Michaelis complex and an acyl-enzyme, were based on steady-state studies and on the observation of individual steps under sub-optimum conditions. In the present paper new methods for the rapid analysis of chemical events and for the spectrophotometric detection of individual steps are applied to these two enzymes. These methods can be used to study reactions with specific amino acid ester substrates. It can be shown that there are at least three distinct steps between the Michaelis complex and the release of ethanol; the latter is likely to correspond to acyl-enzyme formation. The relative rates of these three steps are measured by rapid-flow techniques from observations of the displacement of chromophoric inhibitors and reactions with specific substrates containing chromophores, as well as from ethanol analyses during a single turnover of the enzyme reactions. It is concluded that the reactions of trypsin and chymotrypsin with their specific substrates involve the formation of a specially reactive conformation of the enzyme-substrate complex and that the rate constants involved in this rearrangement are at least as important for the overall reaction as those of the subsequent formation and decomposition of the acyl-enzyme.

Arginine↗
PubMed1966

The catalytic-centre activity and kinetic properties of bovine milk alkaline phosphatase.

1. The phosphorylation of milk alkaline phosphatase was studied under various conditions: maximum incorporation occurred at pH5.0 and 50% incorporation at pH6.6-7.0. 2. The phosphorylation was shown to be specific and the results suggest that the active centre of the enzyme is involved in the process. 3. Phosphoryl-enzyme is rapidly hydrolysed at alkaline pH. at pH7.0 the results suggest that a phosphoryl-enzyme could occur as a transient intermediate in the hydrolysis of phosphate esters by the phosphatase. 4. The catalytic-centre activity of the enzyme was found to be 2700sec.(-1) at pH10.0 and 25 degrees with p-nitrophenyl phosphate as substrate.

Alkaline Phosphatase↗