Abstract
Nonspecific esterases (NsE) of human PNS and CNS occur in free (hydrosoluble) and bound (triton X-100 extractible) forms. Free and bound NsE were studied in whole tissue and in myelin fractions by starch gel electrophoresis (zymograms) and chemical assay, using as substrates alpha-naphthyl acetate, (NA), alpha-naphthyl propionate (NP) and alpha-naphthyl butyrate (NB). By chemical assay whole homogenates of CNS and PNS differ thusly: (1) NP/NA and NB/NA hydrolysis ratios are greater in PNS; (2) NsE activity, whether expressed per gram wet weight or specific activity, is several-fold greater in CNS; (3) 76–86% of NsE activity of PNS occurs in free form while CNS free esterase constitutes less than 20% of the total. NA zymograms of free NsE of PNS and CNS are alike, and differ from other tissues and contain predominantly E-600-resistant A-type esterase, with a minor C-type component. Certain molecular forms of NsE preferentially hydrolyzing NP and NB (and the valerate ester) are characteristic of cerebral and cerebellar white matter and are absent from PNS, liver, kidney, skeletal muscle and leptomeninges. CNS myelin fractions, prepared as described in this publication, contain NsE of predominately B-type (E-600-sensitive enzyme). Respectively, 6.7, 8.0 and 9.1% of the NA-, NP- and NB-hydrolyzing capacity of centrum ovale are recovered in the myelin fraction. PNS myelin lacks NsE. These results, though suggestive, do not prove an intrinsic association of NsE with human CNS myelin. Autolysis, among other factors, may cause displacement of enzyme from in vivo sites. Nonetheless results reported here and in earlier papers support a role for NsE in myelin metabolism, especially of those CNS NsE that cleave preferentially 3–5 carbon esters.
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