[Vitamin B1].
Vitamin B1 (thiamin), taken-up into cells, is converted to thiamin diphosphate (TDP), and TDP acts as a cofactor for several enzymes involving in carbohydrate metabolism. CoA-dependent oxidative decarboxylation of pyruvate is catalyzed by pyruvate dehydrogenase multienzyme complex (PDC) with NAD+ as an electron acceptor in most organisms involving mammals and higher plants. PDC consists of three component enzymes, one of which is pyruvate dehydrogenase (lipoamide) which contains TDP as a prosthetic group. Similar multienzyme complex for 2-oxoglutarate or branched chain 2-oxoacids is also found in mammals. In anaerobic bacteria, archaebacteria and anaerobic protozoa, pyruvate:ferredoxin oxidoreductase (PFOR) functions for the oxidative decarboxylation of pyruvate with ferredoxin in place of NAD+. PFOR contains TDP as a cofactor; however its structure is quite different from PDC and 1-3[4Fe-4S] clusters are involved as redox centers. Pyruvate:NADP+ oxidoreductase (PNOR), which catalyzes the oxidative decarboxylation of pyruvate with NADP+ as an electron acceptor, occurs in mitochondria of Euglena gracilis, a protist containing chloroplasts. PNOR consists of two functional domains, one of which contains TDP and 3[4Fe-4S] clusters and resembles PFOR. Another domain involves FMN and FAD as redox centers and its structure is similar to NADPH-cytochrom P450 reductase.
Inui
H
H
Department of Applied Biological Chemistry, Osaka Prefecture University.
Nakano
Y
Y
D002262:Carboxy-Lyases / Q000378:metabolism; D006801:Humans; D007658:Ketone Oxidoreductases / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D050743:Pyruvate Synthase; D013831:Thiamine / Q000493:pharmacokinetics*
D011768:Pyruvate Dehydrogenase Complex; D007658:Ketone Oxidoreductases; C053164:pyruvate dehydrogenase (NADP+); D050743:Pyruvate Synthase; D002262:Carboxy-Lyases; C021474:2-oxoglutarate decarboxylase; D013831:Thiamine