Bacterial Neutral Protease Research Articles

Immunology and Immunopathology of Legionnaires' Disease

The immune response to the Legionnaires' disease (LD) bacterium has been shown serologically. Recent evidence suggests significant differences in seroreactivity depending on the source of antigen; these data now unequivocally show strain variation for the LD bacterium. Nothing is known about the cellular immune reactivity in patients with Legionnaires' disease. There is little evidence that the lesions and manifestations of the disease are due to immunopathologic mechanisms. Possible explanations for the pathogenesis of pulmonary lesions in Legionnaires' disease include toxic factors, bacterial chemotactic factors, neutral proteases (with complement cleaving activity), lipopolysaccharides, and products of lymphocytes.

32] Leucostoma peptidase A

Publisher Summary Leucostoma peptidase A is the most abundant protease in the venom of the western cottonmouth moccasin (Agkistrodon piscivorus leucostoma) from which it can be isolated in good yield and a high degree of homogeneity. This endopeptidase possesses some characteristics similar to those of bacterial neutral proteases, in as much as it is inhibited by metal complexing reagents, is a metalloprotein that contains calcium and zinc, and has a substrate specificity dictated primarily by the identity of the residue contributing the amino group to the susceptible peptide bond. This chapter deals with an assay procedure which states that Leucostoma peptidase A readily digests casein and denatured hemoglobin, either of which can be used as a substrate to assay the proteolytic activity of fractions obtained during enzyme isolation. It explains the hemoglobin assay for proteolytic activity, arylamidase assay. The chapter also discusses the enzyme isolation, properties such as purity, stability, physical properties, metal content, pH optimum and substrate specificity.

Thermolysin: A zinc metalloenzyme

Metal analyses and inhibitor studies have shown that thermolysin, a neutral protease from B. thermoproteolyticus , is a zinc metalloenzyme. The relevance of this finding to the active site characteristics of other bacterial neutral proteases and to those of alkaline proteases is considered.

The complex active sites of bacterial neutral proteases in relation to their specificities

This chapter describes the activity and the specificity of thermolysin and related bacillus metallopeptidases. The pH-activity profiles of thermolysin and Thermolysin-Like Proteases (TLPs) follow a bell-shaped curve with maximal activity at or near pH 7.0 for both proteolysis. Mature thermolysin comprises 316 residues, forming a bilobal structure in which the N-terminal region is predominantly β-pleated sheet and the C-terminal domain is predominantly α-helical. The catalytically essential zinc atom is located in a deep active-site cleft that lies between the two lobes. The crystallographic studies on thermolysin, coupled with parallel studies on the zinc endopeptidase carboxypeptidase A, have led to a general base mechanism of action being proposed for the zinc peptidase family, with the glutamate of the HEALTH sequence polarizing the zinc-bound water molecule which subsequently attacks the scissile bond. Another histidine residue is proposed to contribute by stabilizing the transition state. Comparison of the crystal structures of thermolysin–ligand complexes with the structure of the free enzyme strongly indicates that thermolysin undergoes a conformational change upon substrate or inhibitor binding.