Muscle acetyl phosphatase

Interconversion processes (see p. 120) also play an important role. They are shown here in detail using the example of the PDH complex (see p. 134). The inactivating protein kinase [la] is inhibited by the substrate pyruvate and is activated by the products acetyl-CoA and NADH+H. The protein phosphatase [Ibj—like isodtrate dehydrogenase [3] and the ODH complex [4j-is activated by Ca. This is particularly important during muscle contraction, when large amounts of ATP are needed. Insulin also activates the PDH complex (through inhibition of phosphorylation) and thereby promotes the breakdown of glucose and its conversion into fatty acids. 

Regulation of the Pyruvate Dehydrogenase Complex In animal tissues, the rate of conversion of pyruvate to acetyl-CoA is regulated by the ratio of active, phosphory-lated to inactive, unphosphorylated PDH complex. Determine what happens to the rate of this reaction when a preparation of rabbit muscle mitochondria containing the PDH complex is treated with (a) pyruvate dehydrogenase kinase, ATP, and NADH (b) pyruvate dehydrogenase phosphatase and Ca2+ (c) malonate. 

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