Characterization of two glyceraldehyde-3-phosphate dehydrogenase isoenzymes from the pentalenolactone producer Streptomyces arenae

Abstract

Pentalenolactone (PL) irreversibly inactivates the enzyme glyceraldehyde-3-phosphate dehydrogenase [D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating)] and is a potent inhibitor of glycolysis in both prokaryotic and eukaryotic cells. PL-producing strain, S. arenae TU469, contains a PL-insensitive glyceraldehyde-3-phosphate dehydrogenase under conditions of PL production. In complex media, no PL production was observed and a PL-sensitive glyceraldehyde-3-phosphate dehydrogenase, rather than the insensitive enzyme, could be detected. The enzymes had the same substrate specificity, but different catalytic and molecular properties. The apparent Km values of the PL-insensitive and sensitive enzymes for glyceraldehyde-3-phosphate were 100 and 250 .mu.M, respectively, and the PL-sensitive enzyme was strongly inhibited by PL under conditions in which the PL-insensitive enzyme was not inhibited. The physical properties of the PL-insensitive enzyme suggest that the protein is an octamer; the PL-sensitive enzyme, like other glyceraldehyde-3-phosphate dehydrogenases, appears to be a tetramer.