Functional analysis of long-chain acyl-CoA thioesterase gene expressed in the brain and testis.

长链酰基-辅酶A硫代酯酶包括许多催化脂肪酰基-辅酶A硫酯水解酶的酶。已有文献证明哺乳动物大脑中对长链酰基-辅酶A有很高的水解活性，提示该酶在这一组织中具有某些特定的作用。然而，它的生理意义仍不清楚。在以往的研究中，我们从大鼠脑胞浆中纯化并鉴定了一种酶，称为BACH(Brain Ayl-CoA hyllase)，通过基因克隆和序列分析，将其鉴定为一种新的长链酰基-CoA硫代酯酶。在大鼠中，巴赫在大脑和睾丸中都有高水平的存在，并占了那里发现的棕榈酰辅酶A水解活性的大部分。为了深入了解Bach的生理功能，我们研究了1.人Bach的特性及其基因结构；2.人Bach基因表达的机制；3.小鼠Bach基因的结构组织；4.Bach在小鼠体内的组织分布；5.建立Bach基因转基因细胞系；以及6.基因打靶。这些发现对了解巴赫的生物化学和分子生物学特性，包括催化和分子特性、组织和亚细胞分布、异构体形成、基因组组织和转录调控非常有用。为进一步研究巴赫函数提供了有用的手段。因此，本研究将为更好地理解巴赫以及这类硫代酯酶的生理意义做出很大贡献。

Long-chain acyl-CoA thioesterases include a number of enzymes that catalyze the hydrolysis of fatty acyl-CoA thioesters to the corresponding free fatty acids and coenzyme A.It has been well documented that there is a markedly high level of hydrolytic activity toward long-chain acyl-CoAs in the brains of mammals, suggesting some specific role of the enzyme in this tissue. However, its physiological significance has remained unclear. In previous studies, we purified and characterized an enzyme, referred to as BACH (brain acyl-CoA hydrolase), from rat brain cytosol, and identified it as a novel long-chain acyl-CoA thioesterase by the cDNA cloning and sequence analysis. In rats, BACH was present at high levels both in the brain and testis, and accounted for the most part of palmitoyl-CoA hydrolyzing activities found there. In this study to gain an insight into physiological function of BACH, we investigated 1. Characteristics of human BACH and its gene structure ; 2. Mechanism of human BACH gene expression ; 3. Structural organization of mouse BACH gene ; 4. Tissue distribution of BACH in the mouse ; 5. Establishment of BACH gene-transfected cell lines ; and 6. Gene targeting. The findings obtained were very informative to understand biochemical and molecular biological properties of BACH, including catalytic and molecular properties, tissue and subcellular distribution, isoform formation, genomic organization, and transcriptional regulation. For further studies of BACH function, useful means were also provided. Thus, the present study will make a large contribution for a better understanding of physiological significance of BACH and probably this class of thioesterases.