FATTY-ACID SYNTHESIS OF AN EICOSAPENTAENOIC AND PRODUCING BACTERIUM -DE-NOVO SYNTHESIS, CHAIN ELONGATION, AND DESATURATION SYSTEMS

The fatty acid synthesis systems of a Shewanella sp., strain SCRC-2738 , that produces a large amount of eicosapentaenoic acid were investiga ted, Two kinds of fatty acid synthesis system, de novo synthesis and c hain elongation ones, were detected in the cytosol. The de novo synthe sis system required an acyl carrier protein, and produced palmitoyl- a nd palmitoleoyl-acyl carrier proteins as final products. The chain elo ngation system also required an acyl carrier protein, and produced an acyl-acyl carrier protein as a product, using palmitoyl-, palmitoleoyl -, stearoyl-, and oleoyl-CoAs as primers but not eicosanoyl- or eicose noyl-CoA, There were an anaerobic pathway and an aerobic desaturation one for the production of unsaturated fatty acids, Eicosapentaenoic ac id seemed to be produced through the aerobic desaturation pathway and not through the anaerobic one, since the latter pathway produced n-7 t ype monoenoic fatty acids, which are different from eicosapentaenoic a cid in the position of the double bond, The desaturase utilized an acy l-acyl carrier protein as a substrate, and this activity increased in the presence of ferredoxin and ferredoxin NADP(+) reductase, Thus, She wanella sp,, strain SCRC-2738, has novel characteristics as to both fa tty acid chain elongation and desaturation systems.