![]() ![]() SM9913 could improve the flavor of frozen meat better than mesophilic proteases by providing additional taste and releasing essential amino acids. showed that cold-adapted protease MCP-01 produced by the deep-sea bacterium Pseudoaltermonas sp. found that the cold-adapted protease purified from Pseudomonas aeruginosa HY1215 showed valuable stability against commercially available surfactants and bleaching agents, which could be evaluated as a cold-washing detergent enzyme. The application of cold-adapted microorganisms and their secreted extracellular cold-adapted proteases has received increasing attention in the last three decades. In order to adapt to the cold living environment, the extracellular proteases produced by the cold-adapted microorganisms also have typical cold-resistance characteristics, such as higher catalytic activity at low temperatures, lower optimal catalytic temperature and higher thermal sensitivity. These microorganisms generally live in the deep sea and the Arctic and South Poles, as well as refrigerators, cold storage and other artificial low-temperature environments. Cold-adapted microorganisms can adapt to low-temperature environments, their optimal growth temperature is around 15 ☌ and they can survive in 0 ☌ or even −20 ☌. Most cold-adapted proteases are produced by cold-adapted microorganisms. Therefore, it remains a challenge to find and develop novel proteases that tolerate one or more extreme conditions.Ĭold-adapted proteases present a class of enzymes that can be catalyzed at a low temperature (the optimum temperature is <40 ☌) with high efficiency, and are usually still active at 0 ☌. However, there are still some limitations in the industrial application of commercial proteases, such as low enzyme activity at low temperature, poor salt tolerance, low tolerance to chemical reagents, single cleavage site, high price and so on. They account for about 2/3 of total enzyme sales worldwide, and are highly favored in detergent, food processing, feed production, peptide synthesis, leather processing and biodegradation industries. Microbial proteases not only play an important role in cellular metabolic processes, but are also important sources of industrial proteases. The vast majority of these proteins are derived from microorganisms. To date, there are 273 different families of protein hydrolases in the MEROPS database. Proteases are a class of enzymes that hydrolyze protein peptide chains and can be divided into different groups according to their active site and catalytic mechanism. Therefore, cold-adapted and salt-tolerant protease EK4-1 offers wide application prospects in the cosmetic and detergent industries. Compared with the homologous proteases EB62 and E423, the cold-adapted protease EK4-1 was more efficient in the proteolysis of grass carp skin, salmon skin and casein at a low temperature, and produced a large number of antioxidant peptides, with DPPH, In addition, the acidic amino acid content of protease EK4-1 was higher than that of the basic amino acid, which might be related to the salt tolerance of protease. Compared with a thermophilic protease Stearolysin, the cold-adapted protease EK4-1 contains more random coils (48.07%) and a larger active pocket (727.42 Å 3). Amino acid composition analysis showed that EK4-1 had more small-side-chain amino acids and fewer large-side-chain amino acids. Mn 2+and Mg 2+ significantly promoted enzyme activity, while Fe 3+, Co +, Zn 2+ and Cu 2+ significantly inhibited enzyme activity. Moreover, EK4-1 is still active in 4 mol/L NaCl solution and is tolerant to surfactants, oxidizing agents and organic solvents furthermore, it prefers the hydrolysis of peptide bonds at the P1’ position as the hydrophobic residues, such as Leu, Phe and Val, and amino acids with a long side chain, such as Phe and Tyr. Ek4-1 has a low optimal catalytic temperature (40 ☌) and is stable at low temperatures. It has the highest sequence similarity with Stearolysin, an M4 family protease from Geobacillus stearothermophilus, with only 45% sequence identity, and is a novel M4 family protease. Mesonia algae K4-1 from the Arctic secretes a novel cold-adapted and salt-tolerant protease EK4-1. ![]()
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