Uemura Takeshi, Tomonari Yuki, Kashiwagi Keiko, Igarashi Kazuei
Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
Biochem Biophys Res Commun. 2004 Mar 19;315(4):1082-7. doi: 10.1016/j.bbrc.2004.01.162.
The product of the UGA4 gene in Saccharomyces cerevisiae, which catalyzes the transport of 4-aminobutyric acid (GABA), also catalyzed the transport of putrescine. The Km values for GABA and putrescine were 0.11 and 0.69 mM, respectively. The UGA4 protein was located on the vacuolar membrane as determined by the effects of bafilomycin A1 and by indirect immunofluorescence microscopy. Uptake of both GABA and putrescine was inhibited by spermidine and spermine, although these polyamines are not substrates of UGA4. The UGA4 mRNA was induced by exposure to GABA, but not putrescine over 12h. The growth of an ornithine decarboxylase-deficient strain was enhanced by putrescine, and both putrescine and spermidine contents increased, when the cells were expressing UGA4. The results suggest that a substantial conversion of putrescine to spermidine occurs in the cytoplasm even though UGA4 transporter exists on vacuolar membranes.
酿酒酵母中UGA4基因的产物催化4-氨基丁酸（GABA）的转运，同时也催化腐胺的转运。GABA和腐胺的Km值分别为0.11和0.69 mM。通过巴弗洛霉素A1的作用和间接免疫荧光显微镜确定，UGA4蛋白位于液泡膜上。尽管这些多胺不是UGA4的底物，但亚精胺和精胺会抑制GABA和腐胺的摄取。UGA4 mRNA在暴露于GABA 12小时后被诱导，但在暴露于腐胺时未被诱导。当细胞表达UGA4时，鸟氨酸脱羧酶缺陷菌株的生长因腐胺而增强，腐胺和亚精胺含量均增加。结果表明，即使UGA4转运体存在于液泡膜上，腐胺在细胞质中也会大量转化为亚精胺。
