Background: Peptidyl-prolyl cis-trans isomerase (PPIases) enzyme plays a vital role in protein folding. It catalyses the cis-trans isomerisation of peptide bonds, an essential step for newly synthesized protein to acquire its correct functional conformation in both prokaryotes and eukaryotes.

Objective: The present study showed the biochemical and molecular characterisation of cyclophilins (PpiB), a type of peptidyl-prolyl isomerases proteins from the pathogenic bacteria Salmonella Typhimurium.

Methods: Salmonella Typhimurium is one of the leading serovars responsible for human and animal salmonellosis globally, with the majority of human cases originating through the food chain. Here successful expression and purification of PpiB protein have been demonstrated and LC-MS based analyses showed high protein score and similarity with other PPi protein. Further the enzymatic activity of the purified recombinant PpiB was determined using Succinyl-Ala-Phe-Pro- Phe-p nitroanilide as substrate and enzyme-catalysed reaction.

Result: Km and Vmax were calculated and found to be Vm = 1.023 ± .06400 min/μg, Km = 0.6219 ± 0.1701 μM, respectively. We have reported for the first time the presence of Salmonella PPIase-B (PpiB) protein isoforms in salmonella genome having PPi activity.

Conclusion: Taken together, our data clearly showed that Salmonella Cyclophilin B (PpiB) protein is active and involved in diverse biological processes and highly similar to the different domain of Cyclophilin proteins.

背景：肽基脯氨酰顺反异构酶（PPIases）酶在蛋白质折叠中起着至关重要的作用。它催化肽键的顺反异构化，这是新合成的蛋白质在原核生物和真核生物中获得其正确功能构象的重要步骤。

目的：本研究显示了致病性鼠伤寒沙门氏菌中一种肽基脯氨酰异构酶蛋白亲环蛋白（PpiB）的生化和分子特征。

方法：鼠伤寒沙门氏菌是全球导致人类和动物沙门氏菌病的主要血清型之一，大多数人类病例来自食物链。在此已经证明了PpiB蛋白的成功表达和纯化，并且基于LC-MS的分析显示出较高的蛋白评分和与其他PPi蛋白的相似性。此外，使用琥珀酰-Ala-Phe-Pro-Phe-p硝基苯胺作为底物和酶催化反应，确定了纯化的重组PpiB的酶活性。

结果：计算出Km和Vmax，分别为Vm = 1.023±.06400 min /μg，Km = 0.6219±0.1701μM。我们首次报道了具有PPi活性的沙门氏菌基因组中沙门氏菌PPIase-B（PpiB）蛋白同工型的存在。

结论：综上所述，我们的数据清楚地表明，沙门氏菌亲环蛋白B（PpiB）蛋白是活跃的，并参与多种生物学过程，并且与亲环蛋白的不同结构域高度相似。