Oxalate as a potent and selective inhibitor of spinach (Spinacia oleracea) leaf NADPH-dependent hydroxypyruvate reductase.
Purified spinach (Spinacia oleracea) NADPH-preferring hydroxypyruvate reductase (HPR-2) was potently and selectively inhibited by oxalate, an end product of metabolism in plants. Both hydroxypyruvate- and glyoxylate-dependent rates of the HPR-2 enzyme were affected. Oxalate acted as an uncompetitive inhibitor of the enzyme, with Ki values of 7 and 36 microM for the NADPH/hydroxypyruvate and NADPH/glyoxylate pairs of reactants respectively. Oxalate, at millimolar levels, caused less than 10% inhibition of purified spinach NADH-preferring HPR (HPR-1) and had no effect on purified spinach NADPH-preferring glyoxylate-specific reductase (GR-1). The inhibition of spinach HPR-2 by oxalate is by far the strongest for any known inhibitor of leaf HPR and GR activities. In photosynthetic tissues, oxalate could potentially act as a primary regulator of extraperoxisomal metabolism of hydroxypyruvate and glyoxylate.
Kleczkowski
L A
LA
Department of Biochemistry, University of Missouri, Columbia 65211.
Randall
D D
DD
Edwards
G E
GE
D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors*; D050537:Hydroxypyruvate Reductase; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D010070:Oxalates / Q000494:pharmacology*; D010944:Plants / Q000201:enzymology*; D013646:Tartronates / Q000494:pharmacology
D010070:Oxalates; D013646:Tartronates; D009249:NADP; D000429:Alcohol Oxidoreductases; D050537:Hydroxypyruvate Reductase