Molecular weight, succinate dehydrogenase

Models, cytochrome c oxidase, 314-315 Molecular weight, succinate dehydrogenase, 232-234 Molybdenum... 

UQ may also be reduced by complex II (succinate ubiquinone oxido-reductase, succinate dehydrogenase), which contains four polypeptide chains, molecular weights 70,000, 27,000, 15,500, and 13,500. The first two constitute bona fide succinate dehydrogenase, a Krebs cycle enzyme catalyzing reaction... 

The succinate dehydrogenase of yeast mitochondria was isolated by Singer et al. 15, 219) in 1957, and stated to have a molecular weight of 200,000 and an iron flavin ratio of 4 1, similar to the mammalian enzyme. These studies antedated, however, the purification of mammalian succinate dehydrogenase by Davis and Hatefi. Therefore, the exact molecular weight and composition of the yeast enzyme will have to be reexamined in light of present information. 

Hatefi et al. 220) have isolated the succinate dehydrogenase of Rhodospirillum ruhrum by extraction of chromatophores with NaC104. The enzyme has two subnits of molecular weights of approximately... 

The mitochondrion is bounded by two pho-spholipid membranes. The outer membrane is freely permeable to molecules, including water, with a molecular weight of up to about 5000. The inner membrane is rich in membrane-bound proteins and consists, in terms of membrane area, of 50% phospholipid and 50% protein (Lenaz, 1988). Pyruvate dehydn>genase, a mitochondrial enzyme, is water soluble. The proteins of the respiratory chain, as well as ATP synthase, are all bound to the inner mitochondrial membrane. The enzymes of the Krebs cycle are water soluble, with the exception of succinate dehydrogenase. This enzyme is bound to the mitochondrial membrane, where it directly funnels electrons, via HAD, to the respiratory chain. 

The prosthetic group of succinic dehydrogenase is a ferroflavoprotein containing one flavin molecule and four iron atoms. The overall molecule is rather large and has a molecular weight of 200,000. As early as 1939, Keilin and Hartree observed that the addition of succinate to a succinic dehydrogenase preparation... 

Mitochondrial cytochrome b was solubilized for the first time by Cooperstein and his associates, and attempts to purify cytochrome b have been made. The enzyme has now been prepared free of cytochrome oxidase, succinic dehydrogenase, and cytochromes c and a. However, the criteria of purity are not always reliable. The best purification procedures have yielded preparations without enzymic activity. In the absence of cationic detergents, the protein tends to aggregate, but with such detergents a minimum molecular weight of 28,000 has been obtained. 

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