Kinetics of gossypol inhibition of bovine lactate dehydrogenase X

Gossypol, a polyphenolic binaphthalene dialdehyde isolated from cotton meal is a potent inhibitor of lactate dehydrogenase-X purified from bovine testis. For the conversion of pyruvate to lactate the IC50 for gossypol is 200 microM for the reverse reaction the IC50 is 12 microM. Gossypol is a competitive inhibitor of NADH, Ki = 30 microM (Km = 17 microM), and NAD+, Ki = 6 microM (Km = 130 microM), and noncompetitive for pyruvate, Ki = 220 microM (Km = 224 microM), and lactate, Ki = 52 microM (Km = 5.6 mM).