Studies on arylsulphatases in the barnacle Balanus eburneus

Arylsulphatases (ASases) have been identified in the mantle tissues of the barnacle Balanus eburneus Gould. This is the first report of these enzymes in the Cirripedia. Using p-nitrocatechol sulphate (NCS) as a substrate, the optimum pH for activity was found to be 5.6 in 0.5 M-acetate buffer, and substrate concentration of 12 mM. The activity of the enzyme was strongly inhibited by phosphate, sulphite and sulphate and not by cyanide, indicating the presence of Type II ASase. Biochemical and electrophoretic studies revealed the coexistence of at least two distinct Type II ASases in the mantle tissues. These are probably similar to the ASase-A and ASase-B reported for vertebrate tissues. The presence of multiple molecular forms of ASase capable of hydrolyzing potassium 6-benzoyl-2-naphthyl sulphate was demonstrated by polyacrylamide gel disc-electrophoresis. The activity patterns of ASases in the mantle tissues were studied in relation to the molt cycle. The activity of ASase-B followed a cyclic pattern which correlated with the molt stages, reaching a maximum in the postmolt. The activity of ASase-A remained essentially the same during the entire molt cycle. Analysis of the activities after dialysis indicates a change in the activity of ASase-B into a non-fluctuating pattern. The enzyme was found in all stages of development, with a ninefold increase in activity in adult forms. The fact that a greater activity was found in the nondigestive organs and that there is an increase in the activity of ASase in tissues of unfed (starved) specimens indicates that the enzyme does not function in the digestive processes, as suggested for other animals by certain investigators. The evidence in this study implicates a major role for dialyzable inhibitory factor(s) as the mechanism involved in the regulation of the activity of ASase-B during the molt cycle. The possible relationship of endogenous phosphate and/or neurosecretory substance(s) with the dialyzable inhibitory factor(s) is discussed. A discussion speculating on the relationship of ASase activity to the cyclic formation and hardening of the exoskeleton and adhesive substance(s) is also presented.