Collagenase, action

Due to the good nucleophilic nature of sulfur, formation of new C—S bonds is relatively easy. This property has been used for intramolecular peptide cyclization 1 and was exploited for preparation of methylenethio ether surrogates, t >[CH2—S], initially as peptide gap inhibitors for blocking collagenase action. 2 These surrogates were later converted into sulfoxide and sulfone derivatives. This expansion of amide replacements compelled a more generalized nomenclature system for pseudopeptides (amides with one or more amide bond surrogates) and led directly to the psi-bracket convention. 1 ... 

Since denatured collagen is susceptible to degradation by nonspecific proteases, proof of specific collagenase action requires the demonstration... 

A topical enzyme aids in the removal of dead soft tissues by hastening the reduction of proteins into simpler substances. This is called proteolysis or a proteolytic action. The components of certain types of wounds, namely necrotic (dead) tissues and purulent exudates (pus-containing fluid), prevent proper wound healing. Removal of this type of debris by application of a topical enzyme aids in healing. Examples of conditions that may respond to application of a topical enzyme include second- and third-degree bums, pressure ulcers, and ulcers caused by peripheral vascular disease An example of a topical enzyme is collagenase (Santyl). 

There are a variety of pathological states in which the action of collagenases is strongly suspected. Some of these disease states are considered briefly below. Since current knowledge concerning the cellular source of the collagenases in these states is often conflicting, a discussion of this subject has been purposely avoided. Instead, possible sources are simply mentioned. 

Klont and Ten Cate (1991) determined the ratio of collagen to calcium for dentin, which is consistent with the ratio of degraded collagen to calcium loss in advanced erosive lesions, while this ratio was lower in incipient lesions. In the initial phase of lesion formation, a relatively large part of the collagen is apparently insusceptible to the action of collagenase. 

Dispase is a neutral protease from Bacillus polymyxa available from Boehringer Corp. Ltd. It is particularly suitable for disaggregation of animal tissues, which seldom suffer from prolonged treatment. It is available alone, or mixed with collagenase. It requires Ca2+ for activity and its action is readily neutralised by EDTA. 

Osteoclasts are multinucleated cells found on the endosteal surface of bone, in Haversian systems and periosteal surfaces. PTH activates osteoclasts (indirectly via osteoblasts that possess PTH receptors). Calcitonin is a potent inhibitor of osteoclast activity. Local cytokine factors, including interleukin-1 (IL-1), tumour-necrosis factor (TNF), TGF- 0 and interferon-y (INF-y), are important regulators. Osteoclast resorption of bone releases collagen peptides, pyridinoline cross-links and calcium from the bone matrix, through the action of lysosomal enzymes (collagenases and cathepsins). The collagen breakdown products in serum and urine (e.g. hydroxyproline) can be used as biochemical markers. 

Figure 9.22 Separation of hydrolysis products of the action of tadpole collagenase on DNP-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Argby reversed-phase HPLC. Upper tracing shows the gradient employed. The reaction was initiated at zero time by the addition of 4 /xg of enzyme. At the indicated times, a 4.0 /xL aliquot erf the reaction mixture was injected onto the HPLC column and the peptides separated. (From Gray and Saneii, 1982.)...

Tetracycline and doxycycline are metalloproteinase inhibitors and when given orally can block the action of corneal collagenases. Either may be effective for resolving noninfected corneal ulcers or corneal melting in which progressive necrosis of stromal tissue occurs despite the absence of a positive culture. Similarly, the anticollagenolytic activity of tetracycline or doxycycline can prove clinically useful in treating persistent corneal epithelial defects. 

Figure 10.5 The effects of lonophore-stimulated human eosinophils on the permeability of bovine bronchial mucosa to mannitol. The inset panel in this figure illustrates the action of 0.05 mgml bacterial collagenase for...

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