Structural and Functional Analysis of the FAS1 Gene Encoding Fatty Acid Synthase β-Subunit in Methylotrophic Yeast Hansenula Polymorpha

Abstract

The biosynthesis of saturated fatty acids is catalyzed by acetyl-CoA carboxylase (ACC) and fatty acid synthetase (FAS). In yeast and lower fungi, the FAS is a heteromultimeric complex of two multifunctional proteins (α6β6) which are encoded by the two unlinked genes, FAS1 (subunit β) and FAS2 (subunit α) (Schweizer et al., 1978). The α-subunit contains three catalytic activities, β-ketoacyl synthase, β-ketoacyl reductase and acyl carrier protein, while the β subunit contains five activities, acetyl transferase (AT), enoyl reductase (ER), dehydrase (DH) and malonyl/palmitoyl transferase (MT/FT) (Stoops et al., 1978). The FAS genes have been cloned from various organisms. It was shown that the sequential order of the catalytic domains is similar only among related species such as yeast and lower fungi (Kajiwara et al., 2001; Kottig et al., 1991; Weisner et al., 1988). The methylotrophic yeast, Hansenula polymorpha, has a great biotechnological potential and is widely used for studying various metabolic pathways such as peroxisome biogenesis and methanol metabolism, and for producing several useful bioproducts (Gellissen, 2002). Recent year, it also has become favorite host to produce recombinant proteins (Faber et al., 1995; Agaphanov et al., 1995). Moreover, H. polymorpha, unlike Saccharomyces cerevisiae, is able to synthesize polyunsaturated fatty acids (UFAs) in addition to mono-UFA (Anamnart et al., 1998). Wishing to use H. polymorpha as an eukaryotic model to study genetic control of saturated and unsaturated fatty acid biosynthesis, we decided to clone H. polymorpha FAS1 gene. In this study, we report the isolation, characterization and functional analysis of H. polymorpha FAS1 gene.