Elastin sources

Chemical Composition. From the point of view of leathermaking, hides consist of four broad classes of proteins coUagen, elastin, albumen, and keratin (3). The fats are triglycerides and mixed esters. The hides as received in a taimery contain water and a curing agent. Salt-cured cattie hides contain 40—50% water and 10—20% ordinary salt, NaCl. Surface dirt is usuaUy about 2—5 wt %. Cattie hides have 5—15% fats depending on the breed and source. The balance of the hide is protein (1). 

The MMPs are a family of zinc-dependent neutral endopep-tidases that share structural domains but differ in substrate specificity, cellular sources, and inductivity (Table I). All the MMPs are important for remodeling of the extra cellular matrix and share the following functional features (/) they degrade extracellular matrix components, including fibronectin, collagen, elastin, proteoglycans, and laminin, (//) they are secreted in a latent proform and require activation for proteolytic activity, (///) they contain zinc at their active site and need calcium for stability, (/V) they function at neutral pH, and (v) they are inhibited by specific tissue inhibitors of metalloproteinases (TIMPs). 

The regulation of the trypsin-like protease Pr2 of M anisopliae was examined by Paterson et al. (1993). Three insoluble protein sources, insect cuticle, elastin and collagen, as well as two soluble proteins, gelatine and especially bovine serum albumin (BSA) were found... 

Amino acid sequences of specific tryptic peptides found in porcine tropoelastin. When tentative assignments are given, the designations are in parentheses. The common repeating units are underlined. In certain instances liberty was taken in defining a common repeating unit when there was only amino acid difference. These sequences are common to the extensible regions in elastin. The tetra, penta or hexa repeats appear to correspond to 15 to 25 percent of the total residues in the protein. The source for the sequence data is reference 1. 

The most ready source of elastin of high purity is the ligamentum nuchae of the larger ruminants, and from this source a protein of constant composition can be isolated by a variety of methods depending on the solubilization and removal of other less inert tissue components. Because of the ease with which it may be isolated the elastin of bovine ligamentum nuchae has come to be regarded as the type standard, but it is by no means certain that elastins from other mammals or other tissues in the same mammal are of identical constitution. 

The kinetics of the enzymatic dissolution of elastin are very complex and the reaction of elastin fibers with elastolytic enzymes is commonly characterized by a lag phase or a markedly sigmoid time course (cf. Hall and Czerkawski, 1959 Naughton et al., 1960). The length of the slow initial phase is influenced by the enzyme-substrate ratio and the source and method of preparation of the elastin used in the assay the course of the reaction with different enzymes is also influenced by the presence or absence of salts, reducing agents, and many other substances. As a result... 

The connective-tissue components collagen and elastin are the probable source of some urinary protein-carbohydrate compounds. A glycopeptide containing approximately equimolar proportions of hy-droxy-L-lysine, D-glucose, and D-galactose has been isolated from... 

The elastic fibrous component of connective tissue, elastin, has often been examined by use of wide-angle diffraction techniques, applied to ligaments as sources of high elastin content. Earliest studies showed collagen-type diffraction (104), and Kolpak (126) found that stretching... 

PJ. Stone, S.M. Morris, S. Griffin, S. Mithieux, A.S. Weiss, Building elastin. Incorporation of recombinant human trc xielastin into extracellular matrices using nonelastogenic rat-1 fibroblasts as a source for lysyl oxidase. Am. J. Respir. Cell Mol. Biol. 24 (2001) 733. 

L.B. Alonso, B.J. Bennion, and V. Daggett, Hydrophobic Hydration is an Important Source of Elasticity in Elastin-based Polymers. J. Am. Chem. Soc., 123,11991-11998,2001. 

Description of the mechanics of elastin requires the understanding of two interlinked but distinct physical processes the development of entropic elastic force and the occurrence of hydrophobic association. Elementary statistical-mechanical analysis of AFM single-chain force-extension data of elastin model molecules identifies damping of internal chain dynamics on extension as a fundamental source of entropic elastic force and eliminates the requirement of random chain networks. For elastin and its models, this simple analysis is substantiated experimentally by the observation of mechanical resonances in the dielectric relaxation and acoustic absorption spectra, and theoretically by the dependence of entropy on frequency of torsion-angle oscillations, and by classical molecular-mechanics and dynamics calculations of relaxed and extended states of the P-spiral description of the elastin repeat, (GVGVP) . The role of hydrophobic hydration in the mechanics of elastin becomes apparent under conditions of isometric contraction. 

---