γ-氨基丁酸具有多种重要的生物学功能，利用乳酸菌生物合成γ-氨基丁酸已成为引人关注的新型技术。近年来有关菌种与工艺方面的研究较多，但对负责合成γ-氨基丁酸的谷氨酸脱羧酶系统的元件组成、结构及其表达调控机制，尚未见深入的工作和报道。我们前期克隆到了高产γ-氨基丁酸的短乳杆菌NCL912的谷氨酸脱羧酶基因（gadB）及其侧翼序列。序列分析表明，谷氨酸脱羧酶系统可能组成操纵子。基于对国内外相关研究进展的了解和前期研究基础，本课题拟进行以下几方面的研究，包括该系统的结构基因（gadCB）和调节基因（gadR）的转录水平；启动子的克隆与鉴定；调控蛋白的纯化及其编码基因的克隆；调控蛋白特异识别的DNA区域及其序列分析；构建突变株NCL912△gadR，并与野生菌gadCB的转录水平和γ-氨基丁酸合成能力进行比较，分析gadR对gadCB转录的调控方式。旨在证实谷氨酸操纵子结构，并探索其表达调。

Gamma-aminobutyric acid has many biological functions. The bio-production of gamma-aminobutyric acid by lactic acid bacteria has become a new interesting biotechnology. However, there are no reports describing the components, structure and expression and regulation mechanism of glutamic acid decarboxylase system responsible for the synthesis of gamma-aminobutyric acid. We have cloned glutamic acid decarboxylase gene (gadB) and its flanking sequences from a high gamma-aminobutyric acid-producer Lactobacillus brevis NCL912. Sequence analysis showed that glutamic acid decarboxylase system may form an operon. Based on the relative research progress and applicant's prophase work, we intend to analyze the relationship of the structural genes and regulatory gene in transcriptional level; clone and identify promoter sequence; purify regulatory protein and clone its encoding gene; obtain specific DNA region binding regulatory protein and get its exact DNA sequence; construct the mutant NCL912△gadR, and compare the transcriptional level of gadCB in NCL912△gadR with that in wild strain NCL912, then analyze the control of gadR on gadCB. The goal of this project is to confirm the operon structure and explore its expression and regulation mechanism.