A simple procedure for the separation of insoluble collagen and elastin

Towards generation of bioactive peptides from meat industry waste proteins: Generation of peptides using commercial microbial proteases

Five commercially available food-grade microbial protease preparations were evaluated for their ability to hydrolyse meat myofibrillar and connective tissue protein extracts to produce bioactive peptides. A bacterial-derived protease (HT) extensively hydrolysed both meat protein extracts, producing peptide hydrolysates with significant in vitro antioxidant and ACE inhibitor activities. The hydrolysates retained bioactivity after simulated gastrointestinal hydrolysis challenge. Gel permeation chromatography sub-fractionation of the crude protein hydrolysates showed that the smaller peptide fractions exhibited the highest antioxidant and ACE inhibitor activities. OFFGEL electrophoresis of the small peptides of both hydrolysates showed that low isoelectric point peptides had antioxidant activity; however, no consistent relationship was observed between isoelectric point and ACE inhibition. Cell-based assays indicated that the hydrolysates present no significant cytotoxicity towards Vero cells. The results indicate that HT protease hydrolysis of meat myofibrillar and connective tissue protein extracts produces bioactive peptides that are non-cytotoxic, should be stable in the gastrointestinal tract and may contain novel bioactive peptide sequences.

Vitamin A deficiency alters pulmonary parenchymal collagen and tissue mechanics

The mechanical properties of the pulmonary parenchyma are strongly influenced by the collagen and elastic fibers that course through the alveolar interstitium and interconnect the bronchovascular bundles. Vitamin A deficiency (VAD) produces effacement and remodeling of the alveolar architecture, resulting in alternating areas of alveolar dilatation and collapse. To better understand the mechanical consequences and reversibility of this remodeling process, we have examined how the remodeling of collagen and elastic fibers correlates with the mechanical properties of the lung parenchyma in VAD rats. An oscillatory impulse was applied at different levels of stress on the fiber network and the tissue damping (G), elastance (H), hysteresivity (G/H, eta) were analyzed. At a supra-physiological functional residual capacity, the lung parenchyma of VAD rats exhibited a lower G and H than Vitamin A sufficient (VAS) rats, which was accompanied by a significant decrease in the quantity of parenchymal collagen and collagen fibers. Retinoic acid (RA) administration restored the parenchymal collagen and mechanical properties.

Evidence for the Maillard reaction in rat lung collagen and its relationship with solubility and age

This study investigated age-related changes in collagen solubility and collagen-linked fluorescence, and their relationship with the Maillard reaction. As a result of the collagen purification of rat lung samples, we obtained two pools of collagen with different degrees of solubility. The relative distribution of collagen between these two fractions was time-dependent, and the proportion of the smaller and less soluble fraction increased with time (r = 0.73, P < 0.0001). In this fraction, the intensity of fluorescence at Exc 335 nm/Em 385 nm, and the total amount of pentosidine increased with age (r = 0.66, P < 0.002, and r = 0.69, P < 0.01, respectively). The mean values for fluorescence and pentosidine per milligram of collagen were, respectively, six and ten times greater in the less soluble fraction. In this fraction the pentosidine per milligram of collagen increased with age (r = 0.59, P < 0.03). Our results demonstrated the presence of pentosidine in rat lung collagen. Moreover, its accumulation in the less soluble fraction suggested a relationship between Maillard reaction products, physico-chemical changes in collagen solubility, and the ageing process in rat lungs.

An elastolytic proteinase from rabbit leukocytes: purification and partial characterization

A proteinase with elastolytic activity was isolated from granules of rabbit bloodstream leukocytes, and purified to apparent homogeneity by a multi-step procedure consisting of ammonium sulfate precipitation, batch fractionation on DEAE-Sephadex A-50, and finally by preparative isoelectric focusing (IEF) on Sephadex G-75 Superfine. The molecule weight of the enzyme, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was 28,500. This enzyme shows an isoelectric point at pH 9.0. The proteinase is active against natural elastins as well as toward Suc-(Ala)3-NA, Methoxy-Suc-(Ala)2-Pro-Val-NA, and (to a lesser extent) against Suc-(Ala)2-Pro-Leu-NA and Boc-Ala-ONp. The inhibition profile of the isolated enzyme indicates that rabbit granulocyte elastase belongs to the group of serine proteinases. Inhibition by some natural proteinase inhibitors is also observed. Unlike other mammalian elastases, it is insensitive to elastatinal.

Salt-soluble collagen and elastin in the human aorta and pulmonary artery

Collagen and elastin, the major structural components of blood vessels, have a very low turnover. In disease, this rate may be increased and an elevation of the tissue concentration of the soluble degradation fragments might be anticipated. In this preliminary study the concentration of extractable collagen and elastin in the aorta and pulmonary artery of eight human subjects postmortem was determined. The proportion of pulmonary artery collagen and elastin that was soluble was generally either equal to or greater than that in the abdominal aorta. The fraction of collagen that was salt extractable was larger than the soluble elastin fraction.

Accumulation and pepsin solubility of collagens in the bowel of patients with Crohn's disease

The collagen content of resected strictured intestine, with and without fistulas, from patients with Crohn's disease has been compared with that in macroscopically normal intestine removed from the same patients and from others without inflammatory bowel disease. Collagen content per unit wet or dry weight of tissue was significantly increased in all grossly diseased tissue whether fistulated or not. Although there was a significant increase in collagen types I, III, and V in diseased tissue, the relative proportions of major collagen types extracted by limited pepsin digestion were similar for both Crohn's and non-Crohn's intestine (type I, 65 to 70 percent; type III, 25 to 30 percent; type IV, 2 to 3 percent; and type V, 2.5 to 3 percent). CNBr digestion of pepsin insoluble material showed a similar relative abundance of types I and III, indicating no major change in collagen type distribution between older (insoluble) and more newly synthesized collagen. There was no evidence of the presence of type I trimer collagen. Type VI collagen, although not quantitated, was observed in 70 percent of intestinal specimens. The proportion of total collagen solubilized by pepsin treatment was significantly greater in both grossly diseased and macroscopically normal Crohn's bowel compared with non-inflammatory bowel disease bowel. These findings suggest that there are disturbances of collagen metabolism in Crohn's intestine, which account for the stricturing process and which may predate gross pathologic changes.

The collagenous protein with elastin crosslinks from Descemet's membrane is not related to type VIII collagen

A collagen-like insoluble protein containing the elastin cross-links (desmosine and isodesmosine) has been isolated from Descemet's membrane. Recently type VIII collagen (endothelial collagen) has been shown to be a major constituent of this membrane. Biochemical studies suggest that these two proteins are unrelated. The cyanogen bromide peptide maps show negligible similarity. Antiserum raised against oxalic acid digests of elastin (alpha-elastin) did not react against an oxalic acid digests of type VIII collagen but did show some reaction against the cross-linked preparation. Immunofluorescent localization has demonstrated the presence of type VIII collagen in trachea but a desmosine cross-linked collagen could not be isolated from this tissue.

The biochemical composition of hemodynamically stressed vascular tissue: the insoluble elastin of experimental arteriovenous fistulae

Arteriovenous fistulae between the external jugular vein and the common carotid artery were surgically fashioned in eight sheep. The altered hemodynamics produced morphological changes similar to those observed in human atherosclerosis. The elastica is a major mural component and undergoes considerable structural variation during lesion development. The most significant biochemical changes in the elastin occur in the experimental vein region. These include a quantitative loss particularly in the midregion of the vein and a decrease in the concentration of up to 20% of the crosslinks (desmosine and isodesmosine). There is an increase in the cholesterol content of the elastin purified from both experimental artery and vein. The bound phospholipid was higher in the experimental artery and in the dilated experimental vein. There was a significant time-dependent loss of elastin in the stressed venous tissue.

The biochemical composition of haemodynamically stressed vascular tissue. III. The collagen composition of experimental arteriovenous fistulae

The external jugular vein and the common carotid artery were anastomosed in 8 sheep. Morphological changes similar to those observed in human atherosclerosis are produced particularly in the venous tissue. There is a significant increase in the collagen content of the dilated mid-segment of the experimental vein. Also there is a positive correlation between post-operative age and the amount of collagen, especially in the distal region of the artery and in the proximal and middle regions of the vein. In both the control and experimental veins the amino acid composition of collagen was very similar. However, the arterial preparations did not exhibit the same degree of purity. Most of the collagen was the type I variant (approx. 80% in arteries and 70% in veins). In the sham-operated veins about 30% of the collagen was type III but it was nearer 17% in the control arteries. Whilst experimental and control arteries had similar proportions of type III collagen, there was a 30% reduction in the experimental veins. Although there was no significant correlation between the proportion of any of the genetic types of collagen and the post-operative age of the animals, there was a strong correlation for the increment in type I in all regions of the experimental vein as a function of time.

The biochemical composition of haemodynamically-stressed vascular tissue. Part 2. The concentrations of protein and connective tissue components in the salt extracts of experimental arteriovenous fistulae

Arteriovenous fistulae were fashioned between the right external jugular vein and the right common carotid artery in seven experimental sheep, which were then grazed for periods up to 4.25 years. Since the morphological changes in the tissue resemble human atherosclerosis, some of the changes in the extractable protein components in this model were studied. In the experimental venous tissue there was a 1.5-2.5 fold increase in salt-soluble protein. The concentration of extractable collagen was 1.5 times higher in the salt extracts of the experimental veins. The concentration of elastin in the extracts from experimental venous tissue was higher than for the sham-operated veins but the experimental arteries yielded lower levels than the contralateral arteries.

The biochemical composition of haemodynamically stressed vascular tissue. Part 1. The lipid, calcium and DNA concentrations in experimental arteriovenous fistulae

Experimental arteriovenous anastomoses were fashioned between the external jugular vein and the common carotid artery in sheep. The altered haemodynamics induced morphological changes, particularly in the venous tissue. Many of these alterations were similar to those seen in human atherosclerosis. Some of the biochemical compositional changes that occurred in such tissues are reported here. Whilst the serum cholesterol level was unaltered during the post-operative period, there was an increase in the free and total cholesterol content of the experimental vein but not of the artery. The serum triglyceride level approximately doubled but the tissue triglyceride rose on only the arterial side of the shunt. There was a decrease in the triglyceride level in the experimental vein. The calcium content showed a slight decrease in both experimental arterial and venous tissue although the drop was not statistically significant. The DNA concentration which was assayed so as to provide a measure of the cell density was about 1.5-2.0 times higher in the arterial tissue.

Salt soluble cross-linked elastin: formation and composition of fibers

Cross-linked elastin has been isolated from the salt extract of sheep vascular tissue by means of hydrophobic interaction chromatography on a column of decyl-agarose. Dialysis of the dimethylformamide and sodium dodecyl sulphate column eluates against distilled water produced a precipitate that was fibrous and that resembled insoluble elastin fibers. As judged by amino acid analyses and SDS-polyacrylamide gel electrophoresis, this precipitation resulted in further purification of the soluble cross-linked elastin. Similar chromatography and precipitation of oxalic acid solubilized cross-linked elastin (alpha-elastin) produced identical results.

Comparison of nonenzymatic glycosylation of arterial and venous collagens

The extent of nonenzymatic glycosylation of collagen isolated from sheep carotid arteries and jugular veins was compared. It was found that the level of this modification in the arterial collagen was about 2.7 times higher than that in the venous collagen. Arteriovenous fistulae were established between the common carotid artery and external jugular vein on one side only of six sheep. Sham arteriotomy and phlebotomy were performed on the contralateral vessels. Although there was an increase in the concentration of these ketoamine-linked hexoses in all the tissue samples assayed, a difference of between two- and three-fold was maintained between the arterial and venous tissue. The relationship of this finding to the development of vascular complications and to the level of circulating reducing sugar is discussed.

Isolation and characterization of salt-soluble cross-linked elastin from vascular tissue

Fibrous elastin, a stable and important constituent of vascular tissue undergoes degenerative changes including fragmentation in atherosclerosis. The nature of the protein fragments produced during the in vivo degradation of elastin is largely unknown. From salt extracts of haemodynamically stressed tissue in sheep, polypeptides were isolated by hydrophobic interaction chromatography. These polypeptides coacervated and had amino acid compositions similar to those of in vitro solubilized elastins. The presence of the cross-links, desmosine and isodesmosine, in the isolated material indicates that the fragments originated from fibrous elastin and that cleavage of cross-links is not necessary for the solubilization of the fibre.

The presence of EC collagen and type IV collagen in bovine Descemet's membranes

When bovine Descemet's membranes (DMs) were characterized after limited pepsinization the major component in DM was found to be endothelial cell (EC) collagen. Phenol extractions of the undigested pepsin residue recovered only type IV collagen. This study provides evidence that EC collagen may be produced by corneal endothelial cells in vivo.

A compilation of amino acid analyses of proteins. XVIII. Residues per thousand residues--5

The amino acid analyses of 213 proteins, as residues per 1000 residues, are given. In addition, the carbohydrate content, the content of any noncommon amino acids, the sources of all proteins, and the necessary literature citations are given.

Purification of salt-soluble cross-linked elastin by hydrophobic interaction chromatography

The hydrophobic protein elastin, which is a major constituent of vascular and lung tissue is fragmented in several pathological conditions. The nature of the soluble fragments is not well understood. Such fragments bind to alkyl chains linked to agarose. Elution, which is effected by dimethylformamide and sodium dodecyl sulphate, is optimal from the decyl-agarose column. Dialysis of the eluates against buffered sodium chloride precipitates elastin, thus further purifying the salt-soluble cross-linked elastin.