Lengi Andrea J, Corl Benjamin A
Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Lipids. 2007 Jun;42(6):499-508. doi: 10.1007/s11745-007-3056-2. Epub 2007 Apr 28.
Stearoyl-CoA desaturase (SCD) is an enzyme responsible for the production of cis-9, trans-11 conjugated linoleic acid in ruminant fats, and for the synthesis of palmitoleoyl-CoA and oleoyl-CoA. To date, only one SCD isoform has been described in ruminant species, although multiple isoforms have been found in many other mammalian species. In this paper, we describe for the first time a second SCD isoform in cattle, which appears to be an ortholog of human SCD5 rather than a homolog of bovine SCD1 or any of the described murine SCD isoforms. As described in other SCD proteins, the predicted amino acid sequence of bovine SCD5 includes four transmembrane domains and three conserved histidine motifs. The amino-terminus of the predicted protein sequence of SCD5 lacks the PEST sequences typically found in SCD1 homologs, which are thought to target proteins for rapid degradation. Similar to human SCD5, the bovine SCD5 gene is organized into five exons and four introns, and is highly expressed in the brain. In other tissues examined, mRNA expression of SCD5 was minimal. Furthermore, the expression levels of SCD5 between brain gray and white matter are not different. This is the first description of a homolog of human SCD5 in a non-primate species.
硬脂酰辅酶A去饱和酶(SCD)是一种负责在反刍动物脂肪中产生顺-9,反-11共轭亚油酸以及合成棕榈油酰辅酶A和油酰辅酶A的酶。迄今为止,在反刍动物物种中仅描述了一种SCD同工型,尽管在许多其他哺乳动物物种中发现了多种同工型。在本文中,我们首次描述了牛中的第二种SCD同工型,它似乎是人类SCD5的直系同源物,而不是牛SCD1或任何已描述的小鼠SCD同工型的同源物。如在其他SCD蛋白中所述,牛SCD5的预测氨基酸序列包括四个跨膜结构域和三个保守的组氨酸基序。SCD5预测蛋白序列的氨基末端缺乏通常在SCD1同源物中发现的PEST序列,这些序列被认为是靶向蛋白质进行快速降解的。与人类SCD5相似,牛SCD5基因由五个外显子和四个内含子组成,并且在脑中高度表达。在检查的其他组织中,SCD5的mRNA表达极少。此外,脑灰质和白质之间SCD5的表达水平没有差异。这是在非灵长类物种中首次描述人类SCD5的同源物。