Partial purification and characterization of the maize mitochondrial pyruvate dehydrogenase complex.
PLANT PHYSIOLOGY 1998;
116:1443-50. [PMID:
9536062 PMCID:
PMC35052 DOI:
10.1104/pp.116.4.1443]
[Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/1997] [Accepted: 12/23/1997] [Indexed: 05/22/2023]
Abstract
The pyruvate dehydrogenase complex was partially purified and characterized from etiolated maize (Zea mays L.) shoot mitochondria. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed proteins of 40, 43, 52 to 53, and 62 to 63 kD. Immunoblot analyses identified these proteins as the E1beta-, E1alpha-, E2-, and E3-subunits, respectively. The molecular mass of maize E2 is considerably smaller than that of other plant E2 subunits (76 kD). The activity of the maize mitochondrial complex has a pH optimum of 7.5 and a divalent cation requirement best satisfied by Mg2+. Michaelis constants for the substrates were 47, 3, 77, and 1 &mgr;m for pyruvate, coenzyme A (CoA), NAD+, and thiamine pyrophosphate, respectively. The products NADH and acetyl-CoA were competitive inhibitors with respect to NAD+ and CoA, and the inhibition constants were 15 and 47 &mgr;m, respectively. The complex was inactivated by phosphorylation and was reactivated after the removal of ATP and the addition of Mg2+.
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