Microbes are an excellent source of enzymes due to their biochemical diversity and their susceptibility to genetic manipulation and they possess almost all the characteristics desired for their biotechnological applications. Microbial proteases are known for its accountability of approximate 40% of the total worldwide enzyme sales.
Bacteria - Most commercial proteases such as neutral and alkaline are produced by Bacillus. Neutral protease is popular for its use in the brewing industry. Their low thermo-tolerance is advantageous for controlling their reactivity during the production of food hydrolysates with a low degree of hydrolysis. Bacterial alkaline proteases are characterized by their high activity at alkaline pH, e.g., pH 10, and their broad substrate specificity with optimal temperature of 60°C. The predominant proteases secreted by Pseudomonas aeruginosa as alkaline proteases. Subtilisins of Bacillus origin is the second largest family of serine proteases with its two different types of alkaline proteases
1). Subtilisin Carlsberg (produced by Bacillus licheniformis) and
2). Subtilisin Novo or bacterial protease Nagase, BPN9 (produced by Bacillus amyloliquefaciens).
The neutral proteases have specificity for hydrophobic amino acids, while the alkaline proteases possess a very broad specificity. Microbes are good source of nautral occurring proteases which are intracellular and extracellular. Aminopeptidases is also type of natural occurring proteases which occur in a wide variety of microbial species including bacteria and fungi. Aminopeptidases are generally intracellular enzymes, but a type of extracellular aminopeptidase is also produced by Aspergillus oryzae. Aminopeptidase I from Escherichia coli is protease with molecular weight of 400 kDa with broad pH optimum of 7.5 to 10.5 and requires magnesium and manganese for optimal activity.
Fungi - Aspergillus oryzae produces acid, neutral, and alkaline proteases which are active over a wide pH range (pH 4 to 11) with broad substrate specificity. Fungal acid proteases have an optimal pH within 4 to 4.5 and are particularly useful in the cheese and bread making industry. Fungal neutral proteases are type of metalloproteases with its optimal pH at 7.0 and are mostyly inhibited by chelating agents.
Viruses - Known examples of viral proteases are serine, aspartic, and cysteine peptidases. Retroviral aspartyl proteases is also required for viral assembly and replication which are expressed as a part of the polyprotein precursor.
About Author / Additional Info:
Author name and address:
Dr. Kirti Rani Sharma,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University Uttar Pradesh, Noida
Sec-125, Gautam Buddha Nagar, Noida-201303 (UP), India.
Email ID: firstname.lastname@example.org, Kirtisharma2k@rediffmail.com