Laboratory of Biomaterials, Swiss Federal Laboratories for Materials Testing and Research (Empa), CH-9014 St. Gallen, Switzerland.
Biomacromolecules. 2009 Apr 13;10(4):916-22. doi: 10.1021/bm801431c.
The regulation of medium-chain-length polyhydroxyalkanoates (mcl-PHA) metabolism in Pseudomonas putida GPo1 was studied by analysis of enzymes bound to PHA granules and enzymes involved in fatty acid oxidation. N-terminal sequencing of granule-bound enzymes revealed the presence of PHA polymerase (PhaC) and PHA depolymerase (PhaZ) and an acyl-CoA synthetase (ACS1), which recently was found to be associated with PHA granules by in vivo study. The acs1 knockout mutant accumulated 30-50% less PHA than its parental strain, confirming the involvement of ACS1 in PHA metabolism. Isolated PHA granules showed both PhaC and PhaZ activities. PhaC activity was found to be sensitive to the ratio of [R-3-hydroxyacyl-CoA]/[CoA] in which free CoA was a mild competitive inhibitor. Fatty acid oxidation was regulated by the [acetyl-CoA]/[CoA] and [NADH]/[NAD] ratios, with high ratios resulting in accumulation and low ratios leading to rapid oxidation of 3-hydroxyacyl-CoA. These results suggest that PHA metabolism is likely to be controlled by the [acetyl-CoA]/[CoA] and [NADH]/[NAD] ratios. The physiological roles of simultaneous PHA accumulation and degradation are also discussed.
聚羟基链烷酸酯（PHA）在铜绿假单胞菌 GPo1 中的代谢调控研究通过分析与 PHA 颗粒结合的酶和参与脂肪酸氧化的酶来进行。颗粒结合酶的 N 端测序揭示了 PHA 聚合酶（PhaC）和 PHA 解聚酶（PhaZ）以及酰基辅酶 A 合成酶（ACS1）的存在，最近的体内研究发现 ACS1 与 PHA 颗粒有关。acs1 敲除突变体积累的 PHA 比其亲本菌株少 30-50%，证实了 ACS1 在 PHA 代谢中的参与。分离的 PHA 颗粒显示出 PhaC 和 PhaZ 活性。发现 PhaC 活性对[R-3-羟酰基辅酶 A]/[辅酶 A]的比值敏感，其中游离辅酶 A 是一种温和的竞争性抑制剂。脂肪酸氧化受[乙酰辅酶 A]/[辅酶 A]和[NADH]/[NAD]比值的调节，高比值导致 3-羟酰基辅酶 A 的积累，低比值导致其快速氧化。这些结果表明 PHA 代谢可能受[乙酰辅酶 A]/[辅酶 A]和[NADH]/[NAD]比值的控制。同时进行 PHA 积累和降解的生理作用也进行了讨论。
