Proteolytic enzymes

About: Proteolytic enzymes is a research topic. Over the lifetime, 23096 publications have been published within this topic receiving 835544 citations.

Phagocytosis and intracellular digestion of collagen, its role in turnover and remodelling

Abstract: Collagens of most connective tissues are subject to continuous remodelling and turnover, a phenomenon which occurs under both physiological and pathological conditions. Degradation of these proteins involves participation of a variety of proteolytic enzymes including members of the following proteinase classes: matrix metalloproteinases (e.g. collagenase, gelatinase and stromelysin), cysteine proteinases (e.g. cathepsin B and L) and serine proteinases (e.g. plasmin and plasminogen activator). Convincing evidence is available indicating a pivotal role for matrix metalloproteinases, in particular collagenase, in the degradation of collagen under conditions of rapid remodelling, e.g. inflammation and involution of the uterus. Under steady state conditions, such as during turnover of soft connective tissues, involvement of collagenase has yet to be demonstrated. Under these circumstances collagen degradation is likely to take place particularly within the lysosomal apparatus after phagocytosis of the fibrils. We propose that this process involves the following steps: (i) recognition of the fibril by membrane-bound receptors (integrins?), (ii) segregation of the fibril, (iii) partial digestion of the fibril and/or its surrounding non-collagenous proteins by matrix metalloproteinases (possibly gelatinase), and finally (iv) lysosomal digestion by cysteine proteinases, such as cathepsin B and/or L. Modulation of this pathway is carried out under the influence of growth factors and cytokines, including transforming growth factor beta and interleukin 1 alpha.

Creation of "amyloid" fibrils from Bence Jones proteins in vitro.

Abstract: "Amyloid" fibrils have been created from some human Bence Jones proteins by proteolytic digestion under physiologic conditions. These fibrils with an antiparallel, β-pleated sheet conformation consist of only a portion of the variable region of the immunoglobulin light polypeptide chain and share the physical properties of amyloid fibrils. The relation between amyloidosis and immunoglobulins is thus more firmly established and a pathogenetic mechanism for amyloid fibril formation is suggested.

Crystalline antigen from the influenza virus envelope.

Abstract: THE envelope of influenza viruses contains two morphologically and chemically distinct glycoproteins, a haemagglu-tinin and a neuraminidase, which recent experiments have indicated1 may be removed from the virion by treatment with the protease, bromelain. In an investigation of the mechanism of this phenomenon it was found that although the neuraminidase protein was completely degraded during proteolysis, the isolated haemagglutinin protein could be recovered almost unchanged from the incubation mixture. We report the subsequent purification and crystallization of the haemagglutinin and its preliminary chemical and antigenic characterization. The X-31 strain of A2/Hong Kong/682 was used in most of the experiments to be described. Viruses were grown in embryonated eggs, purified as described by Skehel and Schild3 and digested with bromelain as described by Compans et al.1. The smooth-surfaced virus particles which resulted were removed from the incubation mixture by centrifuging for 60 min at 100,000g and purified by sucrose density gradient centrifugation (20–60% sucrose in phosphate buffered saline (PBS) (100,000g, 16 h). The morphology of these particles in comparison with intact virus is shown in Fig. 1. It is clear that all of the envelope spike proteins were removed during proteolytic digestion; in agreement with these observations the shaved particles were completely devoid of the haemagglutinating and neuraminidase activities of the virus envelope proteins. Polyacrylamide gel electrophoretic analyses of the polypeptide composition of the particles also indicated that they contained only four of the seven polypeptides of the virus4 in the same proportions as these were present in the intact virus particles (Fig. 2b and c). Both haemagglu-tination and neuraminidase activities were completely destroyed during protease treatment. Electrophoretic analyses of the proteins present in the protease incubation supernatant after removal of the subviral particles indicated, however (Fig. 2a), that the major components of this mixture were two polypeptides of similar mobility to the haemagglutinin polypeptides previously identified3. Thus, the mobility of the larger polypeptide of the supernatant was identical to that of the larger haemagglutinin component and the mobility of the smaller polypeptide indicated a molecular weight difference of approximately 3,000 between this and the smaller haemagglutinin polypeptide.