[The effect of NAD kinase homologues on the beta-oxidation of unsaturated fatty acids with the double bond at an even position in Saccharomyces cerevisiae]

Abstract

ATP-NAD kinase phosphorylates NAD to produce NADP by using ATP, whereas ATP-NADH kinase phosphorylates both NAD and NADH. Three NAD kinase homologues, namely, Utr1p, Pos5p and Utr1p, exist in the yeast Saccharomyces cerevisiae, which were all confirmed as ATP-NADH kinases and found to be important to supply NADP(H) for yeast cells. In S. cerevisiae, fatty acid beta-oxidation is restricted to peroxisomes and peroxisomal NADPH is required for beta-oxidation of unsaturated fatty acids with the double bonds at even positions. Single and double gene disruption strains of NAD kinase genes, i.e., utr1, pos5, yef1, utr1yef1, utr1pos5 and yef1pos5 were constructed by PCR-targeting method. The utilization ability of these mutants for unsaturated fatty acids with the double bonds at even or uneven positions was examined, with wild type BY4742 as positive control cell, and fatty-acyl-CoA oxidase gene deletion mutant (fox1) and peroxisomal NADP-dependent isocitrate dehydrogenase isoenzymes gene deletion mutant (idp3) as negative control cells. The results indicated that the NAD kinase homologues, especially Pos5p, were critical for supplying NADP and then NADPH in peroxisomal matrix. NADP, which was supplied mainly by Utr1p, Pos5p and Yef1p, particularly by Pos5p, was proposed to be able to transfer from outside of peroxisome into peroxisomal matrix and then converted to NADPH by Idp3p.