Acyl-acyl carrier protein as a source of fatty acids for bacterial bioluminescence

Pulse-chase experiments with [(3)H]tetradecanoic acid and ATP showed that the bioluminescence-related 32-kDa acyltransferase from Vibrio harveyi can specifically catalyze the deacylation of a (3)H-labeled 18-kDa protein observed in extracts of this bacterium. The 18-kDa protein has been partially purified and its physical and chemical properties strongly indicate that it is fatty acyl-acyl carrier protein (acyl-ACP). Both this V. harveyi [(3)H]acylprotein and [(3)H]palmitoyl-ACP from Escherichia coli were substrates in vitro for either the V. harveyi 32-kDa acyltransferase or the analogous enzyme ("34K") from Photobacterium phosphoreum. TLC analysis indicated that the hexane-soluble product of the reaction is fatty acid. Phosphate ions and, to a lesser extent, organic alcohols stimulated the rate of acyl-protein cleavage. No significant cleavage of either E. coli or V. harveyi tetradecanoyl-ACP was observed in extracts of these bacteria unless the 32-kDa or 34K acyltransferase was present. Since these enzymes are believed to be responsible for the supply of fatty acids for reduction to form the aldehyde substrate of luciferase, the above results suggest that long-chain acyl-ACP is the source of fatty acids for bioluminescence.