Purification and properties of NADH-specific dihydropteridine reductase from human erythrocytes.
NADH-specific dihydropteridine reductase (EC 1.6.99.7) has been purified from human erythrocytes in essentially homogeneous form. The molecular weight of the enzyme was estimated to be 46,000 by Sephadex G-100 gel filtration. The enzyme reacted with antiserum against NADH-specific dihydropteridine reductase from bovine liver and formed a single immunoprecipitin line in the Ouchterlony double-diffusion system. This precipitin line completely fused with that formed between the human liver enzyme and the antiserum. With use of 5,6,7,8-tetrahydro-6-methylpterin, Km values of the erythrocyte enzyme for NADH and NADPH were determined to be 0.94 and 47 mumol/l, respectively. Vmax values were 58.7 mumol/min/mg with NADH and 6.41 mumol/min/mg with NADPH. The average activity of NADH-specific dihydropteridine reductase of 9 human blood samples from healthy males (20-25 years old) was calculated to be approximately 600 mU/g of hemoglobin, 1.8 mU per 20 microliters of blood, or 1.9 mU per 10(8) erythrocytes.
D000328:Adult; D004093:Dihydropteridine Reductase / Q000097:blood* / Q000302:isolation & purification / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology; D008297:Male; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000097:blood*; D009249:NADP / Q000378:metabolism
D009243:NAD; D009249:NADP; D004093:Dihydropteridine Reductase; D009247:NADH, NADPH Oxidoreductases