Isolation of subunits of citrate lyase and characterization of their function in the enzyme complex.

Citrate lyase [EC 4.1.3.6; citrate oxaloacetate-lyase (pro-3S-CH2-COO--leads to acetate)] from Klebsiella aerogenes has been dissociated with urea; the three different subunits, alpha-chain (molecular weight congruent to 54,000), beta-chain (molecular weight congruent to 32,000), and gamma-chain (acyl carrier protein; molecular weight congruent to 10,000), have been isolated in pure and catalytically active state. Recombination of the three subunits produced citrate lyase that was indistinguishable from the untreated enzyme. The alpha-chain in the presence of acetyl-S-acyl carrier protein catalyzed the formation of the corresponding citryl thioester with liberation of acetate, and the beta-chain catalyzed the cleavage of citryl-S-acyl carrier protein with liberation of oxaloacetate. A simple enzymic method for the preparation of citryl-S-acyl carrier protein is described.