Background: Amidases are ubiquitous enzymes and biological functions of these enzymes vary widely. They are considered to be synergistically involved in the synthesis of a wide variety of carboxylic acids, hydroxamic acids and hydrazides, which find applications in commodity chemicals synthesis, pharmaceuticals agrochemicals and wastewater treatments.

Methods: They hydrolyse a wide variety of amides (short-chain aliphatic amides, mid-chain amides, arylamides, α-aminoamides and α-hydroxyamides) and can be grouped on the basis of their catalytic site and preferred substrate. Despite their economic importance, we lack knowledge as to how these amidases withstand elevated pH and temperature whereas others cannot.

Results: The present study focuses on the statistical comparison between the acid-tolerant, alkali tolerant and neutrophilic organisms. In silico analysis of amidases of acid-tolerant, alkali tolerant and neutrophilic organisms revealed some striking trends as to how amino acid composition varies significantly. Statistical analysis of primary and secondary structure revealed amino acid trends in amidases of these three groups of bacteria. The abundance of isoleucine (Ile, I) in acid-tolerant and leucine (Leu, L) in alkali tolerant showed the aliphatic amino acid dominance in extreme conditions of pH in acidtolerant and alkali tolerant amidases.

Conclusion: The present investigation insights physiochemical properties and dominance of some crucial amino acid residues in the primary and secondary structure of some amidases from acid-tolerant, alkali tolerant and neutrophilic microorganisms.

背景：酰胺酶是普遍存在的酶，这些酶的生物学功能差异很大。它们被认为是协同作用地参与了多种羧酸，异羟肟酸和酰肼的合成，它们在商品化学合成，医药农药和废水处理中得到了应用。

方法：它们水解多种酰胺（短链脂族酰胺，中链酰胺，芳基酰胺，α-氨基酰胺和α-羟基酰胺），并可以根据其催化位点和优选的底物进行分组。尽管它们具有经济重要性，但我们缺乏关于这些酰胺酶如何承受pH和温度升高而其他氨基酸不能承受的知识。

结果：本研究着重于耐酸，耐碱和嗜中性生物之间的统计比较。在对耐酸，耐碱和嗜中性生物的酰胺酶进行的计算机分析中，揭示了氨基酸组成如何显着变化的一些惊人趋势。一级和二级结构的统计分析揭示了这三类细菌的酰胺酶中的氨基酸趋势。耐酸的异亮氨酸（Ile，I）和耐碱的亮氨酸（Leu，L）的丰度表明，在极端的pH条件下，耐酸和耐碱酰胺酶中脂族氨基酸占主导地位。

结论：本研究洞察了来自耐酸，耐碱和嗜中性微生物的某些酰胺酶的一级和二级结构中一些关键氨基酸残基的理化特性和优势。