[Molecular and catalytic properties of bacterial glutamin-(asparagin-)ase]

The review summarizes and analyzes experimental evidence for the properties of glutamine(asparagine)ase from Pseudomonas aurantiaca-548. The enzyme is a tetramer having a molecular weight of 148 kD and consisting of 4 identical subunits having a molecular weight of 37 kD. For glutaminase activity, the optimum pH is in the range of 6.0-8.0, asparaginase activity increases as pH rises. The enzyme is maximally stable at pH 6.8-8.0. The Michaelis constants are 5.3 +/- 0.7 x 10(-6) M for L-glutamine and 5.7 +/- 0.1 x 10(-6) M for asparagine. The reaction products L-aspartate and L-glutamate are competitive inhibitors anazaserine and 6-diase-5-oxo-1-norleucine are classic inhibitors of glutamine(asparagine)ase. The review also presents data on the conditions for culturing Ps. aurantiaca, on the procedures for isolating glutamine(asparagine)ase from biomass of this microbe, on substrate specificity. The results of searching for regulators of catalytic activity, as well as agents enhancing the resistance of enzymes to heat exposures are considered in the paper. Whether the properties of glutamine(asparagine)ase are in conformity with the criteria for primary choice of promising antitumor agents is discussed.