Here, we have analyzed the enzyme ornithine carbamoyltransferase (OCTase) in different classes of microorganisms belonging to psychrophiles, mesophiles and thermophiles. This OCTase catalyzes the formation of citrulline from carbamoyl phosphate (CP) and ornithine (ORN) in arginine biosynthesis pathway and has certain unique adaptations to regulate metabolic pathways in extreme conditions. The tertiary structure of OCTase showed two binding domains, the CP domain and ORN-binding domain at N and C terminals, respectively. We propose general acid–base catalysis in Pseudomonas gessardii between His259 and Asp220 in which later may act as a recipient of proton in the process. The comparative docking analysis showed that substrate-binding loops have been evolved to accommodate their lifestyles across the physiological temperature range where two substrates bind on two distinct loops in psychrophiles and mesophiles, whereas both the substrates bind on a single-substrate-binding loop in thermophiles and bring down the flexibility of the active site pocket to improve its evolutionary fitness.

在这里，我们分析了属于嗜冷菌，嗜温菌和嗜热菌的不同种类微生物中的鸟氨酸氨基甲酰基转移酶（OCTase）。该OCTase催化精氨酸生物合成途径中的氨基甲酸酯磷酸酯（CP）和鸟氨酸（ORN）形成瓜氨酸，在极端条件下具有某些独特的适应性调节代谢途径。OCTase的三级结构分别在N和C端显示两个结合域，即CP域和ORN结合域。我们建议在假单胞菌中进行一般的酸碱催化在His259和Asp220之间，以后可能在此过程中充当质子的接受者。对比的对接分析表明，底物结合环已经进化到适应其在整个生理温度范围内的生活方式，其中在嗜热菌和嗜温菌中，两种底物结合在两个不同的环上，而在嗜热菌中，两种底物结合在单底物结合环上并降低活动位袋的灵活性，以改善其进化适应性。