title: Zinc metalloprotease activity in the cement precursor secretion of the barnacle, Chthamalus fragilis Darwin.
abstract: Adult barnacles, Chathamalus fragilis, were removed carefully from the leaves and stems of marsh grass and floated base-up in algae-supplemented sea water. During the next 24-72 h, the animals secreted onto their exposed bases, a fluid, the cement precursor secretion (CPS), aliquots of which were collected in glass micropipets and pooled. The concentration of protein in pooled samples of CPS averaged 1.5 g +/- 0.42 protein/l of secretion. Protease activity was expressed as A(492) units/h/g of CPS protein. Aliquots of 5-45 l of pooled CPS samples, incubated in the presence of FTC-casein at 37 degrees C for 24 h, exhibited 8.31 x 10(-5) +/- 1.55 x 10(-5) DeltaA(492) units/hr/g of protein on average. Protease activity was optimized by the addition of 10 mM Ca(++) ions. Activity was detectable over a broad pH range, but was optimal around pH 8. Protease activity was inhibited up to 40% in the presence of 2.7 mM ethylenediaminetetraacetic acid (EDTA) and up to 97% in the presence of 2.5 mM 1,10-phenanthroline (OP) in the presence of 10 mM Ca(++) ions. Although low concentrations of Zn(++) ions (10 M) had little effect on protease activity, higher concentrations of Zn(++) ions (50 M to 15 mM Zn(++)) inhibited CPS protease activity. Protease activity was not inhibited by 1 mM phenylmethylsulfonylfluoride (PMSF), nor by 28 M E64, nor by 20 M leupeptin. At the present time, the protease activity in the barnacle CPS may best be characterized as a Ca-stimulated Zn-metalloprotease.
authors.forename: W J
authors.initials: WJ
authors.lastname: Dougherty