Recombinant Production and Characterization of an Extracellular Subtilisin-Like Serine Protease from Acinetobacter baumannii of Fermented Food Origin

Abstract

Acinetobacter baumannii is a ubiquitous bacteria that is increasingly becoming a formidable nosocomial pathogen. Due to its clinical relevance, studies on the bacteria’s secretory molecules especially extracellular proteases are of interest primarily in relation to the enzyme’s role in virulence. Besides, favorable properties that extracellular proteases possess may be exploited for commercial use thus there is a need to investigate extracellular proteases from Acinetobacter baumannii to gain insights into their catalytic properties. In this study, an extracellular subtilisin-like serine protease from Acinetobacter baumannii designated as SPSFQ that was isolated from fermented food was recombinantly expressed and characterized. The mature catalytically active form of SPSFQ shared a high percentage sequence identity of 99% to extracellular proteases from clinical isolates of Acinetobacter baumannii and Klebsiella pneumoniae as well as a moderately high percentage identity to other bacterial proteases with known keratinolytic and collagenolytic activity. The homology model of mature SPSFQ revealed its structure is composed of 10 β-strands, 8 α-helices, and connecting loops resembling a typical architecture of subtilisin-like α/β motif. SPSFQ is catalytically active at an optimum temperature of 40 °C and pH 9. Its activity is stimulated in the presence of Ca 2+ and severely inhibited in the presence of PMSF. SPSFQ also displayed the ability to degrade several tissue-associated protein substrates such as keratin, collagen, and fibrin. Accordingly, our study shed light on the catalytic properties of a previously uncharacterized extracellular serine protease from Acinetobacter baumannii that warrants further investigations into its potential role as a virulence factor in pathogenicity and commercial applications.

Perspectives on Converting Keratin-Containing Wastes Into Biofertilizers for Sustainable Agriculture

“…Recombinant keratinases can be obtained when the sequences are available while the selection of host cells and expression systems are critical because the target protein may not be easily overexpressed (Descamps et al, 2003 ; liu et al, 2013b ; Fang et al, 2014 ; Yong et al, 2020 ; Parinayawanich et al, 2021 ; Yahaya et al, 2021 ). This method is very useful to obtain keratinases with high purify and study the enzymes from pathogenic microorganisms (Muhammed et al, 2021 ). Enzymatic characterization and mutagenesis can be readily studied using recombinant proteins (Zhang et al, 2020 ).…”

Structure, Application, and Biochemistry of Microbial Keratinases

“…Recombinant techniques are applied to the production of keratinases (Descamps et al, 2003;Liu et al, 2013b;Fang et al, 2014;Yong et al, 2020;Yahaya et al, 2021). This method is particularly meaningful for keratinases that are produced by pathogenic microorganisms (Muhammed et al, 2021) and the mutants with an improved enzymatic activity and stability (Zhang et al, 2020). The recombinant production of keratinases does not require the application of keratin as the carbon and nitrogen sources.…”