Abstract

Carbonic anhydrases (CAs, EC 4.2.1.1) have been studied for decades and have been classified as a superfamily of enzymes which includes, up to date, eight gene families or classes indicated with the Greek letters α, β, γ, δ, ζ, η, θ, ι. This versatile enzyme superfamily is involved in multiple physiological processes, catalysing a fundamental reaction for all living organisms, the reversible hydration of carbon dioxide to bicarbonate and a proton. Recently, the ι-CA (LCIP63) from the diatom Thalassiosira pseudonana and a bacterial ι-CA (BteCAι) identified in the genome of Burkholderia territorii were characterised. The recombinant BteCAι was observed to act as an excellent catalyst for the physiologic reaction. Very recently, the discovery of a novel ι-CAs (COG4337) in the eukaryotic microalga Bigelowiella natans and the cyanobacterium Anabaena sp. PCC7120 has brought to light an unexpected feature for this ancient superfamily: this ι-CAs was catalytically active without a metal ion cofactor, unlike the previous reported ι-CAs as well as all known CAs investigated so far. This review reports recent investigations on ι-CAs obtained in these last three years, highlighting their peculiar features, and hypothesising that possibly this new CA family shows catalytic activity without the need of metal ions.

摘要

碳酸酐酶（CA，EC 4.2.1.1）已经研究了几十年，并被归类为酶的超家族，迄今为止，包括八个基因家族或类别，用希腊字母 α、β、γ、δ、ζ 表示, η, θ, ι。这种多功能酶超家族参与多种生理过程，催化所有生物体的基本反应，即二氧化碳可逆地水合为碳酸氢盐和质子。最近，来自硅藻Thalassiosira pseudonana的 ι-CA (LCIP63) 和在Burkholderia territorii基因组中鉴定的细菌 ι-CA (BteCAι)被表征。观察到重组 BteCAι 作为生理反应的极好催化剂。最近，在真核微藻Bigelowiella natans和蓝藻鱼腥藻中发现了一种新型 ι-CA（COG4337）。PCC7120 为这个古老的超家族带来了一个意想不到的特征：这种 ι-CA 在没有金属离子辅因子的情况下具有催化活性，这与之前报道的 ι-CA 以及迄今为止研究的所有已知 CA 不同。这篇综述报告了最近三年获得的 ι-CA 的最新研究，突出了它们的特殊特征，并假设这种新的 CA 家族可能在不需要金属离子的情况下显示出催化活性。