216 Microscopic Histochemistry 



^-Glucuronidase 



The enzyme y3-glucuronidase seems to play an important 

 role in detoxication mechanisms, in the metabolism of phe- 

 nolic steroids/^^ and in the urinary excretion of phenolic 

 compounds. Phenol, camphor, and phenolic steroids are ex- 

 creted, at least in part, as glucuronides. Another interest of 

 the enzyme lies in the fact that malignant tissues often con- 

 tain fairly high concentrations of it.^^^ 



Regular chemical synthesis of glucuronides is a very di£B- 

 cult task; for this reason the substrates are usually prepared 

 by biosynthesis. Rabbits are given phenolic compounds by 

 mouth or intravenously, and the glucuronide is isolated from 

 the urine. 



The histochemical demonstration of glucuronidase is 

 fraught with diflRculties. First of all, even the most active 

 tissues contain very little glucuronidase as compared to 

 other enzymes. A glucuronidase activity of 50 jjM of sub- 

 strate hydrolyzed per gram of tissue per hour is exceptional, 

 whereas the alkaline phosphatase activity of the rat kidney 

 is around 1,000 jjM, and the esterase activity of rat liver 

 4,000-6,000 fxM. Secondly, the enzyme is quite sensitive to 

 fixatives, and this fact makes the use of fresh tissues almost 

 imperative. However, according to recent data of Seligman 

 and co-workers,^^^ fixation in formalin should be possible. 

 Thirdly, the pH optimum of the enzyme is in the acid range, 

 unfavorable for azo-coupling. Friedenwald and Becker^^^ 



127. Fishman, W. H., and Fishman, L. W.: J. Biol. Chem., 152:487, 

 1944; Fishman, W. H.: J. Biol. Chem., 169:7, 1947. 



128. Fishman, V^. H.: Science, 105:646, 1947; Fishman, W. H., and 

 Anlyan, A. J.: Science, 106:66, 1947; Fishman, W. H., and Anlyan, A. J.: 

 Cancer Research, 7:808, 1947; Fishman, W. H., and Anlyan, A. J.: J. Biol. 

 Chem., 169:449, 1947; Odell, L. D., and Burt, J. C: Cancer Research, 

 9:362, 1949; Odell, L. D., Burt, J. C, and Bethea, R.: Science, 109:564, 

 1949. 



129. Seligman, A. M., Chauncey, H. H., and Nachlas, M. M.: Stain 

 Technol, 26:19, 1951. 



130. Friedenwald, J. S., and Becker, B.: J. Cell. & Comp. Physiol., 

 31:303, 1948. 



