Elastase, serine function

The serine proteases are the most extensively studied class of enzymes. These enzymes are characterized by the presence of a unique serine amino acid. Two major evolutionary families are presented in this class. The bacterial protease subtilisin and the trypsin family, which includes the enzymes trypsin, chymotrypsin, elastase as well as thrombin, plasmin, and others involved in a diverse range of cellular functions including digestion, blood clotting, hormone production, and complement activation. The trypsin family catalyzes the reaction ... 

This is a 29-kDa protein that has NH 2-terminal sequence homology with elastase and cathepsin G. However, it contains glycine and not serine at the predicted catalytic site, and so lacks protease and peptidase activity. Purified azurocidin kills a range of organisms (e.g. E. coli, S.faecalis, and C. albicans) in vitro. It functions optimally at pH 5.5 and in conditions of low ionic strength. 

The mammalian serine proteases have a common tertiary structure as well as a common function. The enzymes are so called because they have a uniquely reactive serine residue that reacts irreversibly with organophosphates such as diisopropyl fluorophosphate. The major pancreatic enzymes—trypsin, chymotrypsin, and elastase—are kinetically very similar, catalyzing the hydrolysis of peptides... 

Serine proteases are widely distributed and have many different functions. They are products of at least two evolutionary pathways, which originate in prokaryotes. Many of them resemble trypsin, chymotrypsin, elastase, or sub-tilisin in specificity, but serine proteases with quite different specificities have been isolated recently. A recent NMR study of a bacterial protease labelled with at carbon 2 of its single imidazole groups implicates a buried side chain of aspartic acid as the ultimate base for proton transfers in catalysis and eliminates a charge separation from reaction schemes for catalysis. Much of the catalytic effectiveness of serine proteases can be attributed to substrate binding, but the interactions which yield a Michaelis complex are supplemented by others which stabilize intermediates on the reaction pathway. 

The serine proteases include trypsin, chymotrypsin, and elastase from the pancreas, as well as various proteases from other sources, with functions other than digestion (Voet and Voet, 1995, p. 389fQ. Thus, the protease known as Complement Cl, as obtained from blood serum, is said to be connected with the immune response. 

The polymer passes the tests of compostability, provided that the thickness of the parts do not exceed around 2-3 mm. The extracellular enzymatic degradation consists of two steps a) the enzyme is adsorbed on the polymer surface, through its binding site and b) ester bonds are cleaved through the catalytic site of the enzyme [61]. The polymer chain ends are attacked preferentially. The biodegradation rate is a function of the crystallinity and the content of L-monomers [68]. Some enzymes (proteases) that may degrade PLA are proteinase K, pronase and bromelain. Subtilisin, a microbial serine protease, and some mammalian serine proteases, such as a-chymotrypsin, tr)rpsm and elastase, could also degrade PLA [20, 61, 67]. 

Some endopeptidases are very specific in cleaving peptide bonds. For example, the Staphylococcus aureus V8 endopeptidase will break only that peptide bond whose carbonyl function has been contributed by glutamic acid (in other words the peptide bond must have a glutamic acid residue lying towards the amino terminal end) bovine pancreas elastase will break only those peptide bonds whose carbonyl function is contributed by alanine, glycine, serine, or valine. 

Comparison (or alignment) of amino acid sequences, also called homology search, often provides first-hand information on such conserved structural features and enables one to classify enzymes into families and predict the possible function of a new enzyme (86). A family of enzymes usually folds into similar 3-D structures, at least at the active site region. A typical example is the serine protease family whose members—trypsin, chymotrypsin, elastase, and subtilisin—commonly contain three active-site residues, Asp/His/Ser, which are known as the catalytic triad or charge relay system. Another example is the conserved features of catalytic domains of the highly diverse protein kinase family. In this kinase family, the ATP-binding (or phosphate-anchoring) sites present a consensus sequence motif of Gly-X-Gly-X-X-Gly (67,87). 

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