Regulation of Unsaturated Fatty Acid Synthesis by Low Temperature.

1. 研究了一种嗜冷细菌假单胞菌菌株E-3生物合成不饱和脂肪酸的机理。(1)该细菌的脂肪酸合成酶被证实具有合成不饱和脂肪酸的能力。这种能力被3-癸酰- n -乙酰半胱胺（一种不饱和脂肪酸合成厌氧机制抑制剂）所抑制。(2)该细菌的膜组分具有氧依赖性脂肪酸去饱和活性。(3)不饱和脂肪酸营养缺陷突变体的脂肪酸去饱和活性极低。(4)从以上结果可以看出，这两种机制在该细菌中是共存的，但好氧机制对于该细菌的生存是必不可少的。研究了不饱和脂肪酸顺式到反式异构化与嗜冷细菌弧菌ABE-1的热适应性的关系。(1)从0 ^0 ~ 5^0条件下培养的细胞中提取的细胞磷脂，发现其主要不饱和脂肪酸仅含有顺式棕榈油酸酯。(2)在20^0℃条件下，棕榈油酸酯的反式-反式含量随顺式-反式-反式-反式-反式-反式-不饱和脂肪酸的熔点依次降低，可得出异构化对细菌膜的均粘性有贡献的结论。

1. Mechanism of biosynthesis of unsaturated fatty acid in a psychrotrophic bacterium, Pseudomonas sp. strain E-3, was investigated.(1) Fatty acid synthase from this bacterium was proven to have an ability to synthesize unsaturated fatty acid. This ability was inhibited by 3-decynoyl-N-acetylcysteamine, an inhibitor of anaerobic mechanism for unsaturated fatty acid synthesis.(2) Oxygen-dependent fatty acid desaturate activity was demonstrated in the membrane fraction of this bacterium.(3) It was shown that auxotrophic mutants for unsaturated fatty acid have extremely low activity of fatty acid desaturate.(4) From the above results, it was concluded that the two mechanisms are coexisted in this bacterium, but the aerobic mechanism is indispensable for survival of this bacterium.2. Isomerization of cis-to trans-from of unsaturated fatty acid was investigated in relation to thermal adaptation of a psychrophilic bacterium, Vibrio sp. strain ABE-1.(1) The cellular phospholipid extracted from the cells grown at O^0 to 5^0 was found to contain exclusively cis-from palmitoleate as a main unsaturated fatty acid.(2) Content of trans-from of palmitoleate was increased up to 12% with decreasing the content of cis-from when the cells were grown at 20^0 C.(3) From the fact that melting point of fatty acid decreases in the order of saturated- > trans - > cis-unsaturated form, it was concluded that the isomerization contributes for homeoviscousity of this bacterial membrane.