Efficient carbon dioxide fixation by aromaticcarboxylate decarboxylases catalyzing carboxylation reactions

催化氧化或非氧化脱酸反应的各种酶参与微生物中芳香族羧酸的好氧或厌氧降解。最近，我们发现并鉴定了几种新型的脱羧酶，它们能有效地催化逆羧化反应。在本研究中，我们考察并鉴定了2，3和3，4-二羟基苯甲酸脱羧酶。对脱羧酶进行了纯化，并对其理化性质进行了研究。两种Dacarboxylase均催化以邻苯二酚为底物的逆羧化反应。对脱羧酶基因进行了克隆和分析。根据脱羧酶的一级结构，将脱羧酶分为独立的酶群。此外，我们还考察了热稳定性可逆脱羧酶在超临界二氧化碳中酶固定二氧化碳方面的应用。在超临界二氧化碳中，pH漂移和温度对脱羧酶的羧化活性影响很大。从以4-羟基苯甲酸为唯一碳源的增菌培养物中，分离到具有热稳定的4-羟基苯甲酸脱羧酶的微生物。

Various enzymes catalyzing oxidative or nonoxidative decarboxylation reaction are involved in aerobic or anaerobic degradation of aromatic carboxylic acids in microorganisms. Recently, we found and characterized several kinds of novel decarboxylase, catalyzing the reverse carboxylation reaction efficiently. In the present study, we surveyed and characterized 2,3 and 3,4 dihydroxybenzoate decarboxylases. The decarboxylases were purified to homogeneity, and physicochemicarl properties were investigated. Both dacarboxylases catalyzed the reverse carboxylation reactions for catechol as a substrate. The decarboxylases genes were cloned and analyzed. The decarboxylases were classified into independent enzyme groups on the basis of their primary structures. Furthermore, we surveyed heat stable reversible decarboxylases for the application to enzymatic carbon dioxide fixation in supercritical carbon dioxide. In supercritical carbon dioxide, pH shift and temperature affected the carboxylation activity of decarboxylases severely. From enrichment cultures using 4-hydroxybenzoic acid as a sole carbon source, microorganisms possessing heat-stable 4-hydroxybenzoate decarboxylases have been isolated.