PubMed · 7539621
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J Huggins. 1995. Post-reperfusion coagulopathy.. https://doi.org/10.1093/bja%2F74.5.629-a
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The stratum corneum chymotryptic enzyme (SCCE) has been previously purified from human stratum corneum and resembles a chymotryptic serine endopeptidase involved in physiological detachment of corneocytes from human stratum corneum. From human stratum corneum two inhibitory activities of SCCE could be extracted. These were due to serine protease inhibitors already known to be present in human epidermis, antileukoprotease (secretory leukocyte protease inhibitor) and elafin (skin-derived antileukoprotease). The Inhibition of SCCE by antileukoprotease shows a hyperbolic, mixed type inhibition with an equilibrium dissociation constant of 63 n. Antileukoprotease also inhibits detachment of corneocytes from human plantar callus in vitro almost completely (>96%). In addition, elafin was shown to be a weak inhibitor for SCCE activity, and elafin significantly reduces the shedding of corneocytes. Thus, antileukoprotease, which is known to be produced by human keratinocytes, is likely to be the major physiological inhibitor of SCCE in the epidermis. It seems to be involved in the regulation of desquamation under physiological and pathophysiological conditions.
The recombinant Kunitz protease inhibitor module (domain C5) of human collagen alpha 3(VI) chain was previously shown to lack inhibitory activity for proteases with trypsin-like specificity and some other proteases. We have now prepared mutants in the binding loop region including the P1' site (D2889-->A), the P2' site (F2890-->R) and the P3 site (T2886-->P) and in a more remote region (W2907-->V) either as individual substitutions or combinations of them. These mutants were analyzed for their kinetics of binding to trypsin by surface plasmon resonance and for their capacity to inhibit various proteases. Single substitutions (D-->A, T-->P, W-->V) showed an effect only for D->A which bound to trypsin with Kd = 0.25 microM. A 25-100-fold increase in affinity was observed for the double mutants T-->P/D-->A and F-->R/D-->A and approached the affinity of aprotinin (Kd approximately 0.01 nM) in two different triple mutants. These affinities correlated well with the inhibitory capacities of the mutants for trypsin in the cleavage of a large protein and a small peptide substrate. A similar but not completely identical improvement in inhibitory capacity was also observed for leucocyte elastase but not for thrombin. These data could be interpreted in terms of steric interferences or lack of hydrogen bonding of a few critical residues based on three-dimensional structures available for the C5 domain.
Human angiotensin I-converting enzyme (ACE) exists in intestinal epithelial cells as a membrane-bound (ACEm) and secretory glycoprotein (ACEsec). The electrophoretic mobilities of ACEsec and ACEm on SDS/polyacrylamide gels are similar; the N-deglycosylated ACEsec and ACEm, in contrast, display slight differences in their apparent molecular masses, indicating that the carbohydrate contents of ACEsec and ACEm are different. Moreover, ACEsec is solely N-glycosylated whereas ACEm is N- and O-glycosylated, assessed by lectin binding studies. Spontaneous release of ACEsec is achieved by incubation of brush border membranes at 37 degrees C. Aprotinin, leupeptin and EDTA partly inhibit the generation of ACEsec, strongly suggesting that ACEsec is generated from ACEm by proteolytic cleavage. The expression levels of ACEsec in the intestine may be associated with the differentiation state of mucosal cells. Thus ACEsec is more abundant than ACEm in immature non-epithelial crypt cells of patients with coeliac disease. Well-differentiated epithelial cells, by contrast, contain predominantly ACEm. The variations in the proportions of cleaved ACEsec in differentiated and non-differentiated cells may be due to varying levels of the cleaving protease. Alternatively, because epithelial cell differentiation is accompanied by alterations in the levels of oligosaccharyltransferases, the results suggest a critical role for the glycosylation pattern of ACEm in its susceptibility to the putative cleaving protease.