Patterns of N-acetyl-β-glucosaminidase isoenzymes in the epidermis and hepatopancreas and induction of N-acetyl-β-glucosaminidase activity by 20-hydroxyecdysone in the fiddler crab, Uca pugilator

Abstract

A new staining method for detection of N-acetyl-β-glucosaminidase on denaturing SDS polyacrylamide gels was developed. The isoenzyme pattern of N-acetyl-β-glucosaminidase in the epidermis of the fiddler crab, Uca pugilator, is different from that in the hepatopancreas. Two isoforms of N-acetyl-β-glucosaminidase, with molecular weights of 89 and 45.6 kDa, are present in the hepatopancreas while there is only one form of N-acetyl-β-glucosaminidase, 89 kDa, in the epidermis. No sexual dimorphism was found in these patterns of N-acetyl-β-glucosaminidase isoenzymes. The characteristic isoenzyme patterns in the epidermis and hepatopancreas occurred consistently throughout the molting cycle. Injections of the molting hormone, 20-hydroxyecdysone, at 25 μg/g live weight, into crabs in premolt substage D 1, significantly increased N-acetyl-β-glucosaminidase activity in the epidermis by 86%. Since only one form of N-acetyl-β-glucosaminidase, 89 kDa, is present in the epidermis, the elevation in epidermal enzymatic activity after 20-hydroxyecdysone administration is entirely accounted for by this N-acetyl-β-glucosaminidase isoenzyme. The results reported herein are the first direct evidence that in a crustacean N-acetyl-β-glucosaminidase activity is regulated by the steroid molting hormone.