Genetic evaluation of peroxisomal and cytosolic acetoacetyl-CoA thiolase isozymes in n-alkane-assimilating diploid yeast, Candida tropicalis |
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Authors: | Mitsuyoshi Ueda Naoki Kanayama Atsuo Tanaka |
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Institution: | (1) Laboratory of Applied Biological Chemistry, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, 606-8501 Kyoto, Japan |
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Abstract: | 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 ΔC6 without
a putative C-terminal peroxisomal targeting signal was introduced on CT-T1A locus in the ct-t1bΔ-null mutant. The C-terminus-truncated Thiolase I was active and solely present in the cytosol. Although the ct-t1aΔ/t1bΔ-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 demonstrated 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. |
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Keywords: | Candida tropicalis peroxisome cytosol acetoacetyl-CoA thiolase 3-ketoacyl-CoA thiolase mevalonate |
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