Further studies of human alveolar macrophage alanine-P-nitrophenyl esterase. Evidence of resistance to endogenous antiproteases

The specificity of macrophage elastase on the insulin B-chain

The specificity of macrophage elastase obtained from mouse peritoneal exudative macrophages was determined in the hydrolysis of the oxidized insulin B-chain. This elastase hydrolysed two bonds, namely Ala-Leu and Tyr-Leu. The rate of hydrolysis of the latter was two to three times greater than that of the former. The hexapeptide Glu-Ala-Leu-Tyr-Leu-Val, obtained by cleavage of the insulin B-chain, was not hydrolysed by macrophage elastase. When EDTA was present, proteolysis of the B-chain was not observed. The macrophage elastase is therefore different from the neutrophil elastase in specificity and mechanism.

The location of non-specific esterase in human lung macrophages. An ultrastructural study

The non-specific carboxyl (serine) esterase of the human pulmonary alveolar macrophage was localized ultrastructurally using alpha-naphthyl acetate and hexazotized pararosanilin. The reaction product principally outlined the outer side of the plasma membrane. Consequently, this esterase is an ectoenzyme which may function as mediator of cell response to injurious agents from the outside.