A spectrophotometric cycling assay for reduced coenzyme A and its esters in small amounts of tissue.

Sensitive procedures for the assay of a few pmoles of CoASH and its esters in milligram amounts of tissue are described. The cycling method of Stadtman et al., which involves the arsenolysis of acetyl-P catalyzed by CoA and phosphotransacetylase (PTA), has been used. Selective conversion of various CoA esters to free CoA, followed by oxidation of the CoA so liberated, has enabled the specific assay of CoASH, acetyl CoA, succinyl CoA, and acetoacetyl CoA, and allows partition of the remaining CoA esters into three categories: “other PTA-reactive CoA esters,” probably mostly propionyl CoA; “PTA-unreactive CoA esters plus oxidized CoA;” and long-chain (acid-insoluble) CoA esters. Two inclusive categories are “total acid-soluble CoA” and “total CoA.” Preparation of tissue extracts is described. Rapid tissue fixation is essential for the measurement of cerebral levels of succinyl CoA, which fall 50% or more with decapitation, and of acetyl CoA, which rise 25% when the head is amputated.