ABSTRACT
Proteases are essential constituents found in prokaryotes, fungi, plants, and animals. Proteases are enzymes that are involved in the breakdown of proteins in a process called proteolysis. These enzymes are involved in a multitude of physiological reactions ranging from simple digestion of food proteins to highly regulated cascades. Proteases determine the lifetime of other proteins by playing an important physiological role like hormones, antibodies, or other enzymes. This is one of the fastest switching on and switching off regulatory mechanisms in the physiology of organisms. Several bacteria secrete proteases to hydrolyze the protein peptide bond into simple monomer units. Some of these bacterial proteases also act as an exotoxin, which will destroy the extracellular structures. Proteases play a critical role in many complex physiological and pathological processes such as protein catabolism, blood coagulation, cell growth and migration, tissue arrangement, morphogenesis in development, inammation, tumor growth and metastasis, activation of zymogens, release of hormones and pharmacologically active peptides from precursor proteins, and transport of secretory proteins across membranes (Chambers et al., 2001). In general, extracellular proteases catalyze the hydrolysis of large proteins to smaller molecules for subsequent absorption by the cell, whereas intracellular proteases play a critical role in the regulation of metabolism. Since proteases are physiologically necessary for living organisms, they are ubiquitous, being found in a wide diversity of sources such
10.1 Introduction ........................................................................................................................ 175 10.1.1 Protease enzymes .................................................................................................. 175 10.1.2 Classication of proteases .................................................................................... 176
10.2 Protease inhibitors ............................................................................................................. 176 10.3 Marine microorganisms as a source of metabolites ..................................................... 178
10.3.1 Marine microorganism source of protease inhibitor ....................................... 178 10.3.2 Marine animal source of protease inhibitor ...................................................... 179 10.3.3 Classication of protease inhibitors .................................................................... 180
10.3.3.1 Cysteine protease inhibitors .................................................................. 180 10.3.3.2 Serine protease inhibitors ...................................................................... 181 10.3.3.3 Threonine protease inhibitors ............................................................... 182 10.3.3.4 Aspartic protease inhibitors .................................................................. 183
10.4 Conclusion .......................................................................................................................... 184 References ..................................................................................................................................... 184
as plants, animals, and microorganisms. Besides being necessary from the physiological point of view, proteases are potentially hazardous to their proteinaceous environment and the respective cell or organism must precisely control their activity. When uncontrolled, proteases can be responsible for serious diseases. The control of proteases is generally achieved by regulated expression/secretion and/or activation of proproteases, by degradation of mature enzymes, and by the inhibition of their proteolytic activity (Fitzpatrick and O’Kennedy, 2004).
