PROKARYOTIC CARBONIC ANHYDRASE

说明：碳酸酐酶是一种含锌的酶，可催化 CO和的可逆水合作用在人类中普遍存在，其中酶 参与各种新陈代谢功能。它促进了 释放以HCO3-形式储存的CO，如在红细胞和 二氧化碳跨膜扩散。它还参与了 分泌液，如眼液；事实上，碳酸酐酶抑制剂 是用来治疗青光眼的。过去有关碳酸氢酶的报道 原核生物很少见，主要局限于光养生物，其中酶 为光合作用提供二氧化碳。最近，一类新的碳素 在严格厌氧菌中发现了脱水酶(g类)。 产甲烷古细菌嗜热甲烷单胞菌及其晶体 结构与特征良好的人类酶截然不同。它 假设g碳水解酶在 不同类型非光合作用好氧菌和厌氧菌的生理学研究 古生菌和细菌域。这样做的广泛、长期目标是 项目是为了确定细胞的分布和生理功能。 不同原核生物中的碳酸氢酶。此应用程序有三个 具体目标：(1)确定G碳酸氢酶在 经过选择的生理和系统发育上不同的原核生物。(2) 测定M。碳酸氢酶的生理功能。 嗜热菌在乙酸盐发酵生成甲烷和二氧化碳的过程中。(3) 确定原型g碳酸酐酶的催化机理 来自嗜热菌。这些目标将通过将基因、 生物化学和生物物理研究方法。预计结果将： (一)更好地评估原核生物中碳酸氢酶的程度，(二) 鉴定自然界中碳酸酐酶的新生理功能， 以及(Iii)对所有碳素的催化机理提供了新的见解 脱水酶，特别是G类。

DESCRIPTION: Carbonic anhydrase is a zinc-containing enzyme which catalyzes the reversible hydration of CO and is ubiquitous in humans where the enzyme participates in an assortment of metabolic functions. It facilitates in the liberation of CO stored in the form of HCO3- as in red cells and in the diffusion of CO2 across membranes. It is also involved in the formation of secretory fluids such as ocular fluid; indeed, carbonic anhydrase inhibitors are used to treat glaucoma. Past reports of carbonic anhydrase in procaryotes have been rare and largely confined to phototrophs where enzyme supplies CO2 for photosynthesis. Recently, a new class of carbonic anhydrase (the g class) was discovered in the strictly anaerobic methane-producing archaeon Methanosarcina thermophila with a crystal structure strikingly distinct from the well-characterized human enzymes. It is hypothesized that the g carbonic anhydrases have novel roles in the physiology of diverse nonphotosynthetic aerobes and anaerobes from the Archaea and Bacteria domains. The broad, long-term objective of this project is to determine the distribution and physiological function of carbonic anhydrases in diverse procaryotes. This application has three specific aims: (1) Ascertain the occurrence of g carbonic anhydrases in selected physiologically and phylogenetically diverse procaryotes. (2) Determine the physiological function of the carbonic anhydrase from M. thermophila in the pathway of acetate fermentation to methane and CO2. (3) Determine the catalytic mechanism of the prototypic g carbonic anhydrase from M. thermophila. These goals will be achieved by integrating genetic, biochemical and biophysical research methods. The results are expected to: (i) better assess the extent of carbonic anhydrases in procaryotes, (ii) identify novel physiological functions for carbonic anhydrases in nature, and (iii) provide new insights into the catalytic mechanism of all carbonic anhydrases and the g class in particular.