Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany.
Environ Microbiol Rep. 2011 Aug;3(4):443-8. doi: 10.1111/j.1758-2229.2010.00214.x. Epub 2010 Sep 30.
The amino acid proline is not only synthesized as a compatible solute but also used as a carbon and energy source by the moderately halophilic bacterium Halobacillus halophilus. Growth on proline was not affected by the salinity of the medium. Proline was degraded by proline dehydrogenase (ProDH) and Δ(1) -pyrroline-5-carboxylate dehydrogenase (P5CDH) to glutamate via Δ(1) -pyrroline-5-carboxylate. The basic biochemical parameters for ProDH and P5CDH activities were obtained for both in cell free extracts. The encoding genes were identified. H. halophilus has two isogenes each for prodh and p5cdh. prodh2 and p5cdh2 form an operon (put operon) whose mRNA is highly abundant in proline-grown cells. Expression of the put operon was also upregulated by salinity and late growth phase in glucose-grown cells. Similarly, ProDH and P5CDH activities increased in late exponential growth phase. This observation is in line with the previous notion that the compatible solute proline is degraded in stationary phase (in glucose grown cultures).
氨基酸脯氨酸不仅作为相容性溶质合成，而且还被中度嗜盐细菌盐杆菌用作碳源和能源。脯氨酸的生长不受培养基盐度的影响。脯氨酸通过脯氨酸脱氢酶（ProDH）和Δ（1）-吡咯啉-5-羧酸脱氢酶（P5CDH）降解为谷氨酸，通过Δ（1）-吡咯啉-5-羧酸。获得了无细胞提取物中 ProDH 和 P5CDH 活性的基本生化参数。鉴定了编码基因。盐杆菌的 prodh 和 p5cdh 各有两个同工酶。prodh2 和 p5cdh2 形成一个操纵子（put 操纵子），其 mRNA 在脯氨酸生长的细胞中高度丰富。在葡萄糖生长的细胞中，盐度和生长后期也上调了 put 操纵子的表达。同样，ProDH 和 P5CDH 活性在指数生长后期增加。这一观察结果与先前的观点一致，即相容性溶质脯氨酸在静止期（在葡萄糖生长的培养物中）降解。
