222 A SYMPOSIUM ON RESPIRATORY ENZYMES 



tamic acid and oxalacetic acid was noted in the presence of malo- 

 nate, succinate, pyrophosphate, and citrate (14). 



In contrast to the above findings with di- and tribasic acids 

 Braunstein (1) reported that small concentrations of dibasic acids 

 competitively inhibit "catalytic" transamination. The latter refers 

 to the catalytic effect of small concentrations of a dibasic alpha- 

 amino or alpha-keto acid on transamination between a monobasic 

 alpha-amino acid and a monobasic alpha-keto acid. The author's 

 attempts to corroborate this finding of Braunstein's have not been 

 successful (10, 14). 



Vysshepan (47) found that the activity of glutamic aminopherase 

 was inhibited by the following reagents (molar concentrations): 

 quinone (0.01); potassium cyanide (0.01); glutathione (0.002-0.004); 

 cations of calcium, barium, and strontium (0.02); mercury and silver 

 (0.0001). Reagents which are relatively harmless are narcotics, so- 

 dium fluoride, monoiodo- and monobromo-acetic acids, arsenite, 

 arsenate and selenite; the anions, chloride, bromide, iodide, acetate, 

 nitrate, carbonate, sulfate (0.01); ascorbic acid (0.01), hydrogen 

 sulfide, cysteine, ferrous ion, semicarbazide, phenylhydrazine and 

 hydroxylamine. Sober and Cohen (64) observed no inhibition of 

 transaminase by glutathione (0.005 M.). 



It is apparent that thus far no specific inhibitor is available for 

 transaminase. The discovery of such a compound would aid greatly 

 in elucidating the physiological role of transamination. 



JF/ormones.— Transamination with purified transaminase and the 

 system glutamic acid plus oxalacetic acid is uninfluenced by high 

 concentration of the following: insulin (crystalline and zinc com- 

 pounds), desoxycorticosterone, cortical extract, anterior pituitary 

 extract, estradiol, androsterone, testosterone, and stilbestrol (63). 



Carcinogens.— No effect on transaminase activity was observed 

 with methylcholanthrene and dimethylaminoazobenzene (63). 



Vitamins.— Thiamin and cocarboxylase are without influence on 

 transaminase activity (63). However, a decrease in activity was ob- 

 served in minced breast muscle from B^ deficient pigeons with the 

 system glutamic acid plus pyruvic acid (63). Similar findings have 

 recently been published by Kritzmann (48). Barron (49), on the 

 other hand, found no decrease in transamination in liver from Bj 

 deficient rats. These results are not necessarily contradictory, since 

 Ban'on and his coworkers employed somewhat different experi- 

 mental conditions (personal communication). Investigations are at 



