612 



2. ANALOGS OF ENZYME REACTION COMPONENTS 



ther work on the exact^mechanism of this inhibition might provide interest- 

 ing information. Wylie et al. (1960) found pyrogallol to be the most potent 

 inhibitor of a series of polyphenols and epinephrine analogs, inhibiting 50% 

 at 0.03 mM when epinephrine is 0.3 mM. However, gallate, adrenalone, and 

 arterenone are almost as active. A new inhibitor of 0-methyltransferase was 

 studied briefly by D'lorio and Mavrides (19^3). This is 3.5-diiodo-4-hy- 

 droxybenzoate and it inhibits the rat liver enzyme competitively with 

 Ki = 0.013 mM. 



Inhibition of the Oxidation of Aromatic Compounds by Bacteria 



The metabolism of o-nitro- and p-nitrobenzoate by Nocardia is quite 

 strongly inhibited by m-nitrobenzoate, o-nitrophenol, and p-nitrophenol 

 (Cain, 1958). The competitive nature of this interference was demonstrated 

 by reciprocal plotting. The enzymes involved here are not well characterized 

 and, indeed, the action could be on a transport mechanism at the mem- 



+ 100 



+ 50 



% 



CHANGE 



-50 



-100 



METANEPHRINE 



AND 



NORMETANEPHRINE 



30 



DAYS 



Fig. 2-23. Effects of pyrogallol injected subcutaneously 



at a dose of 20 mg/kg on the urinary excretion of free 



and methylated catecholamines by rabbits. (From 



Nukada et al, 1962.) 



