14] Fatty acid reductase from Photobacterium phosphoreum

Abstract

This chapter discusses the fatty acid reductase from Photobacterium phosphoreum . Fatty acid reductases from bioluminescent bacteria are responsible for the synthesis of long-chain aldehydes used as substrates in the luciferase-catalyzed luminescent reaction. Both ATP and NADPH are required for the reduction of fatty acids. The purified fatty acid reductase from Photobacterium phosphoreum is a multienzyme complex consisting of three distinct subunits (designated as 58K, 50K, 34K), which are synthesized in concert with luciferase during luminescence induction in the late stages of bacterial growth. Two of the components, an acyl-protein synthetase (50K) and a reductase (58K), are essential for fatty acid reductase activity, while the third component (34K), an acyltransferase, appears to be involved in channeling of fatty acids into this reaction. The acyl-protein synthetase catalyzes the ATP-dependent activation of fatty acids to form a tightly bound acyl-AMP (carboxyphosphate anhydride) intermediate that can acylate the synthetase (50K) component. The reduction of acylated 50K polypeptide with NADPH is catalyzed by the reductase (58K) component of the complex, converting the activated fatty acid to aldehyde. The 58K component can be assayed independently using acyl-CoA as a substrate, and has thus been referred to as acyl-CoA reductase.