Purification and Characterization of D-Glucosaminate Dehydratase from Pseudomonas fluorescens(Biological Chemistry)

概要

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D-Glucosaminate dehydratase (EC 4.2.1.26) from Pseudomonas fluorescens (IFO 14808) was purified to homogeneity, as judged by the criterion of a single band on disc-gel electrophoresis. The enzyme (molecular weight 61,000) consisted of two subunits identical in molecular weight (about 30,000). Pyridoxal 5'-phosphate was an essential cofactor for the enzyme. The enzyme catalyzed the dehydration of D-glucosaminate and of several D- and L-hydroxyamino acids. Especially when the concentration of substrate was low, D-serine was dehydrated at a rate similar to the rate of dehydration of D-glucosaminate. If both substrates were added to the reaction mixture at the same time, the rate of the reaction was additive until their individual concentrations reached to 0.2m M level. However, as the concentrations of both the substrates were increased, the rate fell below the rate recorded with D-glucosaminate only. The kinetics of this reaction (in the presence of 1〜10mM D-GlcNA) demonstrate that D-glucosaminate dehydratase is inhibited both non-competitively (at low concentrations) and competitively by D-serine. From these and other observations, we postulate the presence of a binding site specific for D-serine on the enzyme.
社団法人日本農芸化学会の論文
1989-10-23