Kamisaka Y, Nakahara T
Applied Microbiology Department, National Institute of Bioscience and Human-Technology, Ibaraki.
J Biochem. 1994 Dec;116(6):1295-301. doi: 10.1093/oxfordjournals.jbchem.a124678.
Diacylglycerol acyltransferase (DGAT) was examined as a key enzyme for triacylglycerol (TG) accumulation of an oleaginous fungus, Mortierella ramanniana var. angulispora. Subcellular fractionation of the fungus showed that DGAT activity was highest in the lipid body fraction, which occupied 77% of the recovered DGAT activity. DGAT activity in the lipid body fraction was much higher than that in the membrane fraction in terms of both total activity and specific activity. Similar results were obtained with another homogenization method. After repeated washing of the lipid body fraction, DGAT activity in the lipid body fraction was still larger than those in other fractions. The lipid body fraction contained larger amounts of lipids, especially TG and diacylglycerol. Moreover, the lipid body fraction had a specific set of polypeptides at 24, 29, and 59 kDa. These analyses of lipid and polypeptide composition suggested that the lipid body fraction represented a specific intracellular structure, presumably the lipid body. DGAT activity in the lipid body fraction had a similar characteristics to that in the membrane fraction, although some differences in sensitivity to SH-reagents were observed. Increase in DGAT activity in the lipid body fraction was observed when lipids were accumulated in the fungus. On the other hand, DGAT activity in the lipid body fraction decreased when lipids were accumulated with an increase in carbon to nitrogen ratio in media.
二酰甘油酰基转移酶（DGAT）被作为一种产油真菌拉曼被孢霉变种角孢霉中三酰甘油（TG）积累的关键酶进行了研究。该真菌的亚细胞分级分离显示，DGAT活性在脂质体部分最高，脂质体部分的DGAT活性占回收总活性的77%。就总活性和比活性而言，脂质体部分的DGAT活性远高于膜部分。用另一种匀浆方法也得到了类似结果。对脂质体部分进行反复洗涤后，脂质体部分的DGAT活性仍高于其他部分。脂质体部分含有大量脂质，尤其是TG和二酰甘油。此外，脂质体部分含有一组特定的分子量分别为24、29和59 kDa的多肽。这些脂质和多肽组成分析表明，脂质体部分代表一种特定的细胞内结构，推测为脂质体。脂质体部分的DGAT活性与膜部分的DGAT活性具有相似的特性，尽管在对巯基试剂的敏感性上存在一些差异。当真菌中脂质积累时，脂质体部分的DGAT活性增加。另一方面，当脂质随着培养基中碳氮比的增加而积累时，脂质体部分的DGAT活性降低。
