Genetic evaluation of peroxisomal and cytosolic acetoacetyl-CoA thiolase isozymes in n-alkane-assimilating diploid yeast, Candida tropicalis.
The n-alkane-assimilating diploid yeast, Candida tropicalis, possesses two acetoacetyl-CoA thiolase (Thiolase I) isozymes encoded by one allele: peroxisomal and cytosolic Thiolase Is encoded by both CT-T1A and CT-T1B. To clarify the function of peroxisomal and cytosolic Thiolase Is, the site-directed mutation leading Thiolase I delta C6 without a putative C-terminal peroxisomal targeting signal was introduced on CT-T1A locus in the ct-t1b delta-null mutant. The C-terminus-truncated Thiolase I was active and solely present in the cytosol. Although the ct-t1a delta/t1b delta-null mutants showed mevalonate auxotrophy, the mutants having the C-terminus-truncated Thiolase I did not require mevalonate for growth, as did the strains having cytosolic Thiolase I. These results demonstrate that the presence of Thiolase I in the cytoplasm is indispensable for the sterol synthesis in this yeast. It is of greater interest that peroxisomal and cytosolic Thiolase I isozymes, products of the same genes, play different roles in the respective compartments, although further investigations will be necessary to analyze how to be sorted into peroxisomes and the cytosol.
Ueda
M
M
Laboratory of Applied Biological Chemistry, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan. miueda@sbchem.kyoto-u.ac.jp
Kanayama
N
N
Tanaka
A
A
D000101:Acetyl-CoA C-Acetyltransferase / Q000235:genetics* / Q000378:metabolism*; D000473:Alkanes / Q000378:metabolism; D002175:Candida / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D003600:Cytosol / Q000201:enzymology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D020675:Peroxisomes / Q000201:enzymology* / Q000235:genetics
D000473:Alkanes; D007527:Isoenzymes; D000101:Acetyl-CoA C-Acetyltransferase