Abstract
Keratinase can specifically attack disulfide bridges in keratin to convert them from complex to simplified forms. Keratinase thermal stability has drawn attention to various biotechnological industries. In this study, a keratinase DgeKer was identified from a slightly thermophilic species, D. geothermalis. The in silico analysis showed that DgeKer is composed of signal peptide, N-terminal propeptide, mature domain, and C-terminal extension. DgeKer and its C-terminal extension-truncated enzyme (DgeKer-C) were cloned and expressed in E. coli. The purified DgeKer and DgeKer-C showed maximum activity at 70 °C and pH 9–The thermal stability assay (60 °C) showed that the half-life value of DgeKer and DgeKer-C were 103.45 min and 169.10 min, respectively. DgeKer and DgeKer-C were stable at the range of pH from 9 to 11 and showed good tolerance to some metal ions, surfactants and organic solvent. Furthermore, DgeKer could degrade feathers at 70 °C for 60 min. However, the medium became turbid with obvious softening of barbules after being treated with DgeKer-C, which might be due to C-terminal extension. In summary, a thermostable keratinase DgeKer with high efficiency degradation of feathers may have great potential in industry.
Highlights
Keratinase (EC3.4.21/24/99.11) is a class of enzymes that can degrade keratin, which is a structural protein used by animals for mechanical protection with sulfur-containing compounds and disulfide bonds
Many keratinases have been identified from microorganisms, but the number of keratinases used in the market is very small, which might be related to the thermal stability of keratinases [9]
The amino acid sequence of DgeKer was compared with those of keratinases, which were KerA from Bacillus licheniformis PWD-1, MtaKer from M. taiwanensis WR-220 and aqualysin-I from Thermus aquaticus YT-1 in Figure 1 It was proposed that DgeKer consists of four parts, including signal peptide (Pre), N-terminal pro-peptide (N-pro), mature domain with a three highly conserved catalytic triad residues which is formed by Asp171, His203 and Ser354
Summary
Keratinase (EC3.4.21/24/99.11) is a class of enzymes that can degrade keratin, which is a structural protein used by animals for mechanical protection with sulfur-containing compounds and disulfide bonds. It can degrade feathers and other difficult-to-degrade keratinous substances with low energy consumption and environmental friendliness, which has application potential in husbandry [1,2], medical [3,4,5], cosmetics, biological materials [6] and other industries. In the process of feather degradation, higher temperatures are favorable for the destruction of disulfide bonds in keratin, which improves hydrolysis efficiency. It is very important to find and identify high temperature-adaptive keratinases
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