Regulation of Unsaturated Fatty Acid Synthesis by Low Temperature.

1.研究了耐冷菌假单胞菌E-3菌株合成不饱和脂肪酸的机理。(1)脂肪酸合成酶被证明具有合成不饱和脂肪酸的能力。这种能力被3-癸炔酰基-N-乙酰基半胱胺抑制，3-癸炔酰基-N-乙酰基半胱胺是不饱和脂肪酸合成的厌氧机制的抑制剂。(2)氧依赖性的脂肪酸去饱和的活动，证明在该细菌的膜部分。(3)结果表明，不饱和脂肪酸营养缺陷型突变体具有极低的脂肪酸去饱和酶活性。(4)以上结果表明，两种机制在该菌中共存，但好氧机制是该菌生存所必需的.研究了一株嗜冷菌（Vibrio sp. strain ABE-1）的不饱和脂肪酸顺式到反式异构化与热适应的关系。(1)从0^0 ~ 5^0 ℃培养的细胞中提取的细胞磷脂中只含有顺式棕榈油酸酯作为主要的不饱和脂肪酸。(2)当细胞在20 ℃生长时，随着顺式油酸酯含量的降低，反式油酸酯的含量增加到12%。(3)从脂肪酸的熔点以饱和- >反- >顺-不饱和形式的顺序降低的事实可以得出结论，异构化有助于这种细菌膜的等粘性。

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.