He Z, Wiegel J
Department of Microbiology, University of Georgia, Athens 30602-2605, USA.
Eur J Biochem. 1995 Apr 1;229(1):77-82. doi: 10.1111/j.1432-1033.1995.tb20440.x.
A 4-hydroxybenzoate decarboxylase from the anaerobe Clostridium hydroxybenzoicum strain JW/Z-1T was purified and partially characterized. It had an apparent molecular mass of 350 kDa and consisted of six identical subunits of 57 kDa each. The temperature optimum for the decarboxylation was approximately 50 degrees C, the optimum pH 5.6-6.2. The pI of the enzyme was 5.1. The activation energy for decarboxylation of 4-hydroxybenzoate was 65 kJ.mol-1 (20-37 degrees C). The enzyme also catalyzed decarboxylation of 3,4-dihydroxybenzoate. The apparent Km and kcat values obtained for 4-hydroxybenzoate were 0.40 mM and 3.3 x 10(3) min-1, and for 3,4-dihydroxybenzoate 1.2 mM and 1.1 x 10(3) min-1, respectively, at pH 6.0 and 25 degrees C. The enzyme activity was not influenced by the addition of biotin or avidin to either the crude cell extracts or the purified enzyme. The p-hydroxyl group of hydroxybenzoate appears to be essential for binding by the enzyme. The N-terminal amino acid sequence shows some similarity to the uroporphyrinogen decarboxylases from Synechococcus and Saccharomyces. The enzyme catalyzed the reverse reactions, that is, the carboxylation of phenol to 4-hydroxybenzoate and of catechol to 3,4-dihydroxybenzoate. The carboxylation did not require ATP.
对厌氧菌羟基苯甲酸梭菌JW/Z-1T菌株中的一种4-羟基苯甲酸脱羧酶进行了纯化及部分特性鉴定。其表观分子量为350 kDa，由六个相同的57 kDa亚基组成。脱羧反应的最适温度约为50℃，最适pH为5.6 - 6.2。该酶的等电点为5.1。4-羟基苯甲酸脱羧反应的活化能为65 kJ·mol-1（20 - 37℃）。该酶还催化3,4-二羟基苯甲酸的脱羧反应。在pH 6.0和25℃条件下，4-羟基苯甲酸的表观Km和kcat值分别为0.40 mM和3.3×10³ min-1，3,4-二羟基苯甲酸的分别为1.2 mM和1.1×10³ min-1。向粗细胞提取物或纯化酶中添加生物素或抗生物素蛋白均不影响酶活性。羟基苯甲酸的对羟基似乎是酶结合所必需的。N端氨基酸序列与集胞藻属和酿酒酵母属的尿卟啉原脱羧酶有一些相似性。该酶催化逆反应，即苯酚羧化为4-羟基苯甲酸以及邻苯二酚羧化为3,4-二羟基苯甲酸。羧化反应不需要ATP。
