Davé B A, Vaughn R H
J Bacteriol. 1971 Oct;108(1):166-74. doi: 10.1128/jb.108.1.166-174.1971.
A strain of Bacillus pumilus produced an extracellular pectic enzyme with polygalacturonic acid as the substrate. This enzyme, with optimal activity at pH 8.0 to 8.5, produced reaction products that strongly absorbed light at 232 nm, indicating the presence of a pectic acid trans-eliminase (PATE). Neither pectin esterase nor polygalacturonase was detected in the cell-free culture fluid. Chromatographic examination of the end products revealed the presence of large quantities of unsaturated oligouronides unlike those found with B. polymyxa. It was found that the PATE was produced extracellularly during the negative logarithmic death phase of the organism. The filtrate from sonically treated cells did not show any activity for PATE or hydrolases for lower oligogalacturonides at any time during the growth cycle. The enzyme was inducible. Pectin, National Formulary (NF) was the best inducer, followed by polygalacturonic acid and galacturonic acid. Enzyme activity was markedly stimulated by calcium and other divalent ions. Copper and cobalt ions were inhibitory. The partially purified enzyme showed no significant activity on pectin containing a high methoxyl content (96% esterified). However, pectin NF with a lower methoxyl content (68% esterified) was attacked to a degree by the partially purified and crude enzyme preparations. The initial rate of PATE activity increased up to 60 C, about 16-fold higher than that observed at room temperature. The activation energy was calculated as 12,183 cal/mole. A protective action of calcium chloride against heat inactivation of the PATE was observed. Degradation of polygalacturonic acid by this enzyme produced several unsaturated oligouronides soon after its addition to the substrate. The major endproduct was thought to be different from that of other known PATE enzymes. Paper chromatographic studies and viscosity measurements disclosed the random cleaving nature of the enzyme an endo-PATE.
一株短小芽孢杆菌以聚半乳糖醛酸为底物产生了一种胞外果胶酶。该酶在pH 8.0至8.5时活性最佳，其反应产物在232 nm处有强烈的光吸收，表明存在果胶酸反式消除酶（PATE）。在无细胞培养液中未检测到果胶酯酶和聚半乳糖醛酸酶。对终产物的色谱分析表明，存在大量不饱和低聚寡糖醛酸，这与多粘芽孢杆菌产生的不同。研究发现，PATE是在该生物体的负对数死亡期胞外产生的。经超声处理的细胞滤液在生长周期的任何时候都未显示出PATE或低聚半乳糖醛酸水解酶的活性。该酶是可诱导的。果胶、美国国家处方集（NF）是最佳诱导剂，其次是聚半乳糖醛酸和半乳糖醛酸。钙和其他二价离子可显著刺激酶活性。铜离子和钴离子具有抑制作用。部分纯化的酶对高甲氧基含量（96%酯化）的果胶没有显著活性。然而，低甲氧基含量（68%酯化）的果胶NF会受到部分纯化和粗酶制剂的一定程度攻击。PATE活性的初始速率在60℃时增加，比室温下观察到的速率高约16倍。计算出的活化能为12,183卡/摩尔。观察到氯化钙对PATE热失活有保护作用。该酶添加到底物后不久，聚半乳糖醛酸就被降解产生了几种不饱和低聚寡糖醛酸。主要终产物被认为与其他已知的PATE酶不同。纸色谱研究和粘度测量揭示了该酶（一种内切PATE）的随机切割性质。
