428 2. ANALOGS OF ENZYME REACTION COMPONENTS 



It was previously stated that /^-glucuronidases do not seem to partici- 

 pate in glucuronide synthesis in tissues and the evidence is mainly the 

 lack of inhibition by glucaro-l,4-lactone usually observed (Levvy and 

 Marsh, 1960). For example, Lathe and Walker (1958) found no effects of 

 2 mM glucaro-l,4-lactone on the formation of o-aminophenylglucuronide 

 or bilirubin-glucuronide in liver suspensions. However, Fishman and Green 

 (1957) reported that glucarate potently inhibits glucuronyl transfer (50% 

 inhibition by 0.05 mM), and Sie and Fishman (1954) found glucarate and 

 glucurone to inhibit glucuronide synthesis in liver slices. It is not definitely 

 known if these inhibitions relate to a /^-glucuronidase or a transferase, but 

 the question of the role of the /^-glucuronidases in glucuronide synthesis 

 should probably be left open. 



The urinary bladder cancer that occurs in people employed in certain 

 industries may be related to the formation of glucuronides of aromatic 

 amines in the body and their subsequent hydrolysis by urinary /5-glucur- 

 onidase. The oral administration of inhibitory analogs to patients is a 

 possible approach to the prevention of such cancers. Boy land et al. (1957) 

 found that the urinary enzyme can be inhibited by administration of glu- 

 conate and glucarate at a dose of 10 g/day, but the most potent inhibition 

 is produced by glucaro-l,4-lactone, 73% inhibition occurring from 1.5-2 

 g/day and 90% inhibition from 4 g/day. Nevertheless, these inhibitions are 

 less than expected and the urinary pH was reported later to be an important 

 factor, the inhibition decreasing as the pH rises above 6 (Boyland et al., 

 1959). Inhibition of liver /^-glucuronidase in mice by the administration 

 of glucaro-l,4-lactone at doses from 50 to 800 mg/kg (17% to 76%) was 

 found by Akamatsu et al. (1961). The maximal inhibition occurs at 30-60 

 min and after 2-4 hr most of the activity has returned. Similar results 

 were found in rat liver and kidney. Since /^-glucuronidase and /?-iV-acetyl- 

 glucosaminidase hydrolyze products from chondroitin and hyaluronate and 

 may participate in the metabolism of connective tissue mucoproteins, and 

 since certain tumors have relatively large amounts of these enzymes, Carr 

 (1963) administered the two inhibitors — glucaro-l,4-lactone and 2-acet- 

 amido-2-deoxygluconolactone — to mice bearing Tumor 2146. At 150 mg/kg 

 these substances are nontoxic and cause regression of the tumors. It was 

 suggested that the inhibitors prevent the penetration of the tumor cells 

 through the intercellular cement substance, but this is admittedly only a 

 tenuous hypothesis. Whatever the explanation, it represents an interesting 

 approach to tumor chemotherapy. 



Inhibition of Various Glycosidases by Glucono- and Glucaro Lactones 



The inhibition of the /^-glucuronidases by the saccharo-l,4-lactones sug- 

 gested that the /^-glycosidases might be inhibited by the aldonolactones, 

 and this was found to be so by Conchie (1953, 1954). A sheep rumen /?- 



