Correa García S, Bermúdez Moretti M, Ramos E, Batlle A
Centro de Investigaciones sobre Porfirinas y Porfirias, CIPYP (CONICET, FCEyN, UBA), Ciudad Universitaria, Pabellón II, Buenos Aires, Argentina.
Int J Biochem Cell Biol. 1997 Aug-Sep;29(8-9):1097-101. doi: 10.1016/s1357-2725(97)00047-2.
Evidence has been obtained showing that transport of delta-aminolevulinic acid (ALA), a precursor of porphyrin biosynthesis in Saccharomyces cerevisiae, is mediated by the gamma-aminobutyric acid (GABA)-specific permease, UGA4. In yeast GABA is also incorporated by the general amino acid permease (GAP1) and the specific proline permease (PUT4). The aim of the present work was to carry out a comparative study on the regulation of ALA and GABA transport to confirm our proposal that both compounds share the UGA4 permease. ALA and GABA uptake were measured in cells grown on minimal media with different carbon and/or nitrogen sources. To study the effect of the carbon source on UGA4 permease, ALA and GABA incorporation were measured in D27 strain, lacking GAP1 permease, and grown in proline as the sole nitrogen source, so the activity of PUT4 permease was negligible. The effect of the nitrogen source on UGA4 permease was studied measuring ALA and GABA uptake rates in cells from media with ammonium, proline and urea as nitrogen sources. It was found that the regulation by the carbon source was similar on ALA and GABA transport; they depend equally on the energetic conditions of the cells. Moreover, regulation by the nitrogen source on ALA and GABA uptake was also similar, and identical to that described already for UGA4 permease. These results are further evidence that both compounds, ALA and GABA, share the GABA-specific permease, UGA4.
已有证据表明，酿酒酵母中卟啉生物合成的前体δ-氨基乙酰丙酸（ALA）的转运是由γ-氨基丁酸（GABA）特异性通透酶UGA4介导的。在酵母中，GABA也可通过通用氨基酸通透酶（GAP1）和特异性脯氨酸通透酶（PUT4）摄入。本研究的目的是对ALA和GABA转运的调控进行比较研究，以证实我们提出的这两种化合物共用UGA4通透酶的观点。在以不同碳源和/或氮源的基本培养基上生长的细胞中测量ALA和GABA的摄取。为了研究碳源对UGA4通透酶的影响，在缺乏GAP1通透酶且以脯氨酸作为唯一氮源生长的D27菌株中测量ALA和GABA的摄入，因此PUT4通透酶的活性可忽略不计。通过测量以铵、脯氨酸和尿素作为氮源的培养基中的细胞对ALA和GABA的摄取速率，研究氮源对UGA4通透酶的影响。结果发现，碳源对ALA和GABA转运的调控相似；它们同样依赖于细胞的能量状况。此外，氮源对ALA和GABA摄取的调控也相似，且与已描述的UGA4通透酶的调控相同。这些结果进一步证明，ALA和GABA这两种化合物共用GABA特异性通透酶UGA4。
