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Purification and Characterization of Glucose Dehydrogenase from a Heterotrophically Grown Blue-Green Alga ¹

Janet L. Gibson^b and F. Robert Tabita^b

^a Marine Science Laboratory, University of Texas at Austin, Port Aransas, Texas 78373, ^b Department of Microbiology, University of Texas at Austin, Austin, Texas 78712

NADP- and NAD-dependent glucose dehydrogenase was partially purified from a dark-grown blue-green alga (endophytic Nostoc strain MAC). Polyacrylamide gel electrophoresis established that a single protein possessed dual activity for either NADP or NAD. No other electron acceptor substituted for pyridine nucleotides and no evidence for a flavin prosthetic group was found. Although the Km for NADP was 8.8 µM and for NAD 328 µM, the enzyme was equally active with NAD or NADP at saturating levels of substrates. The enzyme was similar to previously described glucose dehydrogenase in that it had a high Km for glucose (18-20 mM at 35 C) and an alkaline pH optimum of 7.6 to 9.4.