THE CLEAVAGE OF TYROSYL PEPTIDES BY PEPSIN FROM COLLAGEN SOLUBILISED BY THE NISHIHARA TECHNIQUE

The triple helix of collagens - an ancient protein structure that enabled animal multicellularity and tissue evolution

The cellular microenvironment, characterized by an extracellular matrix (ECM), played an essential role in the transition from unicellularity to multicellularity in animals (metazoans), and in the subsequent evolution of diverse animal tissues and organs. A major ECM component are members of the collagen superfamily -comprising 28 types in vertebrates - that exist in diverse supramolecular assemblies ranging from networks to fibrils. Each assembly is characterized by a hallmark feature, a protein structure called a triple helix. A current gap in knowledge is understanding the mechanisms of how the triple helix encodes and utilizes information in building scaffolds on the outside of cells. Type IV collagen, recently revealed as the evolutionarily most ancient member of the collagen superfamily, serves as an archetype for a fresh view of fundamental structural features of a triple helix that underlie the diversity of biological activities of collagens. In this Opinion, we argue that the triple helix is a protein structure of fundamental importance in building the extracellular matrix, which enabled animal multicellularity and tissue evolution.

Inexpensive α-amylase production and application for fiber splitting in leather processing

Recently, the production of superior quality enzymes using waste sources has promoted greater research interest due to their enhanced enzyme activity, selectivity and stability.

A rapid assay to measure collagen synthesis in cell cultures

Limited pepsin digestion and precipitation of resistant parts of proteins with perchloric acid on glass-fiber filters has been used as a rapid way to determine the radioactive collagen secreted into fibroblast culture media. The specificity of the pepsin cleavage was tested by digesting [14C]- or [3H]proline- and [3H]tyrosine-labeled procollagens. Radioactivities obtained with this method were comparable with those obtained with collagenase digestions or hydroxyproline determinations. Dialysis of the samples is avoided and the radioactive collagen can thus be determined from the small medium samples obtained from microtest plates. The method was used to localize a collagen synthesis-increasing factor in preparative isoelectric focusing of microphage culture media.

Pepsin-solubilized collagen of human nucleus pulposus and annulus fibrosus

Human nucleus pulposus and annulus fibrosus, obtained at autopsy from patients 7-30 years of age, were extracted with 2 M guanidine-HCl (pH 5.82) to remove proteoglycans, then stirred with pepsin in 0.5 M acetic acid, followed by three 24-h extractions with 1 M NaCl (pH 7.5) and one 24-h extraction with 2 M KSCN (potassium thiocyanate) (pH 7.2). Pepsin and NaCl solubilized an average of about 30% of nucleus pulposus collagen and 18% of annulus fibrosus collagen. KSCN extracted a further 34% of nucleus pulposus collagen and only 4% of annulus fibrosus collagen. CM-cellulose chromatography of nucleus and annulus collagen purified from the pepsin, NaCl and KSCN supernatants consistently revealed only one peak, always appearing slightly ahead of the alpha1 position for rat tail tendon type I collagen. Polyacrylamide and SDS-gel electrophoresis consistently revealed only one band with the mobility of alpha1 chains. Amino acid composition of collagen from nucleus and annulus is comparable to those of mammalian and avian cartilage type II collagen, and distinctly different from those of rat tail tendonand guinea pig skin type I collagens. Periodate oxidation of nucleus and annulus collagens showed that 81% and 67%, respectively, of the hydroxylysine residues survive treatment, compared to 71% for bovine articular cartilage collagen and 17% for guinea pig skin collagen. Total hexose analysis revealed 1.8 muM and 2.0 muM hexose per muM periodate-stable hydroxylysine in nucleus and annulus collagens, respectively. Ion exchange chromatography showed the presence of glucose and galactose in a ratio of 0.92:1 in nucleas collagen and 1.07:1 in annulus collagen. Pepsin-solubilized, NaCl-extracted collagen from nucleus and annulus formed native-type fibrils in vitro. The banding patterns of ATP-induced segment-long-spacing precipitates of nucleus and annulus collagens were identical to each other and indistinguishable from those of cartilage (type II) collagen, but distinctly different from those of rat tail tendon (type I) collagen. These data suggest that the collagen which can be extracted after limited pepsin attack of human nucleus and annulus is of the form [alpha1 (II)]3.

Oblique banding pattern in collagen fibrils reconstituted in vitro after trypsin treatment

Collagen fibres from rat tail tendon suspended in small pieces in a solution (pH 7.8) containing 0.5 M CaCl2 were treated with purified bovine trypsin at 20 degrees C for 20 h. After the enzyme treatment collagen from this solution was precipitated out and reconstituted in vitro into native-type fibrils. The banding pattern in these reconstituted fibrils was found to be oblique. This is comparable to that observed recently in fibrils reconstituted from cartilage collagen. On the other hand, normal transverse banding pattern was observed in the fibrils reconstituted in vitro from collagen solution of rat tail tendon which was not pre-treated with trypsin. No significant change was, however, observed in the segment long spacing fibrils precipitated from the enzyme-treated collagen solution. It is possible that the enzyme might affect the mode of organization of tropocollagen molecules during in vitro fibrillogenesis into native-type fibrils either by interacting with the "telopeptide" regions or with the non-collagenous components associated with the native protein and this could probably result into the formation of fibrils with oblique banding pattern.

Cathepsin B1. A lysosomal enzyme that degrades native collagen

1. Experiments were made to determine whether the purified lysosomal proteinases, cathepsins B1 and D, degrade acid-soluble collagen in solution, reconstituted collagen fibrils, insoluble collagen or gelatin. 2. At acid pH values cathepsin B1 released (14)C-labelled peptides from collagen fibrils reconstituted at neutral pH from soluble collagen. The purified enzyme required activation by cysteine and EDTA and was inhibited by 4-chloromercuribenzoate, by the chloromethyl ketones derived from tosyl-lysine and acetyltetra-alanine and by human alpha(2)-macroglobulin. 3. Cathepsin B1 degraded collagen in solution, the pH optimum being pH4.5-5.0. The initial action was cleavage of the non-helical region containing the cross-link; this was seen as a decrease in viscosity with no change in optical rotation. The enzyme also attacked the helical region of collagen by a mechanism different from that of mammalian neutral collagenase. No discrete intermediate products of a specific size were observed in segment-long-spacing crystalloids (measured as native collagen molecules aligned with N-termini together along the long axis) or as separate peaks on gel filtration chromatography. This suggests that once an alpha-chain was attacked it was rapidly degraded to low-molecular-weight peptides. 4. Cathepsin B1 degraded insoluble collagen with a pH optimum below 4; this value is lower than that found for the soluble substrate, and a possible explanation is given. 5. The lysosomal carboxyl proteinase, cathepsin D, had no action on collagen or gelatin at pH3.0. Neither cathepsin B1 nor D cleaved Pz-Pro-Leu-Gly-Pro-d-Arg. 6. Cathepsin B1 activity was shown to be essential for the degradation of collagen by lysosomal extracts. 7. Cathepsin B1 may provide an alternative route for collagen breakdown in physiological and pathological situations.

Pepsin treatment of avian skin collagen. Effects on solubility, subunit composition and aggregation properties

1. Collagen was extracted from chick skin with dilute acetic acid followed by dilute acetic acid containing pepsin. 2. The solubilized collagens were purified and portions subjected to further digestion by pepsin. 3. This treatment decreased the aldehyde content but contamination by hexosamine was not diminished. 4. Pepsin treatment converted practically all the acid-soluble collagen into monomeric subunits (alpha-chains), but the pepsinsolubilized material retained a significant amount of higher subunits (beta- and gamma-chains). 5. Treatment lowered the rate of fibrillogenesis by acid-soluble collagen, but was without effect on pepsin-solubilized collagen.