[47] Mammalian succinate dehydrogenase

This chapter discusses the four aspects of mammalian succinate dehydrogenase: (1) a critical comparison of assay methods, (2) activation–deactivation of the enzyme, (3) the active site of the enzyme, and (4) the comparison of the properties of various purified preparations including recent improvements of procedures for isolating the reconstitutively active form in high yield and with a high turnover number. Because the catalytic turnover of succinate dehydrogenase is faster than the rate-limiting step in the respiratory chain, artificial electron acceptors are usually used for assays of the enzyme in order to ensure that full activity is being measured. Of these, phenazine methosulfate (PMS) with either DCIP or cytochrome c as the terminal oxidant, may be used with the particulate or soluble preparations. Ferricyanide has been widely used for the assay of succinate dehydrogenase. Polarographic or manometric measurements of the succinate–PMS reaction are not recommended, as they are less sensitive and the rate is limited by the oxygen concentration.