Ueda Mitsuyoshi, Kanayama Naoki, Kamasawa Naomi, Osumi Masako, Tanaka Atsuo
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.
Biochim Biophys Acta. 2003 Mar 17;1631(2):160-8. doi: 10.1016/s1388-1981(03)00002-7.
In the yeast Candida tropicalis, two thiolase isozymes, peroxisomal acetoacetyl-CoA thiolase and peroxisomal 3-ketoacyl-CoA thiolase, participate in the peroxisomal fatty acid beta-oxidation system. Their individual contributions have been demonstrated in cells grown on butyrate, with C. tropicalis able to grow in the absence of either one. In the present study, a lack of peroxisomal 3-ketoacyl-CoA thiolase protein resulted in increased expression (up-regulation) of acetoacetyl-CoA thiolase and other peroxisomal proteins, whereas a lack of peroxisomal acetoacetyl-CoA thiolase produced no corresponding effect. Overexpression of the acetoacetyl-CoA thiolase gene did not suppress the up-regulation or the growth retardation on butyrate in cells without peroxisomal 3-ketoacyl-CoA thiolase, even though large amounts of the overexpressed acetoacetyl-CoA thiolase were detected in most of the peroxisomes of butyrate-grown cells. These results provide important evidence of the greater contribution of 3-ketoacyl-CoA thiolase to the peroxisomal beta-oxidation system than acetoacetyl-CoA thiolase in C. tropicalis and a novel insight into the regulation of the peroxisomal beta-oxidation system.
在热带假丝酵母中，两种硫解酶同工酶，即过氧化物酶体乙酰乙酰辅酶A硫解酶和过氧化物酶体3-酮酰基辅酶A硫解酶，参与过氧化物酶体脂肪酸β-氧化系统。它们各自的作用已在以丁酸盐为碳源生长的细胞中得到证实，热带假丝酵母在缺乏其中任何一种酶的情况下都能生长。在本研究中，缺乏过氧化物酶体3-酮酰基辅酶A硫解酶蛋白导致乙酰乙酰辅酶A硫解酶和其他过氧化物酶体蛋白的表达增加（上调），而缺乏过氧化物酶体乙酰乙酰辅酶A硫解酶则没有产生相应的影响。在没有过氧化物酶体3-酮酰基辅酶A硫解酶的细胞中，乙酰乙酰辅酶A硫解酶基因的过表达并不能抑制丁酸盐上的上调或生长迟缓，尽管在丁酸盐生长细胞的大多数过氧化物酶体中检测到大量过表达的乙酰乙酰辅酶A硫解酶。这些结果提供了重要证据，表明在热带假丝酵母中，3-酮酰基辅酶A硫解酶对过氧化物酶体β-氧化系统的贡献大于乙酰乙酰辅酶A硫解酶，并为过氧化物酶体β-氧化系统的调控提供了新的见解。
