IV. BIOCHEMICAL SYSTEMS 353 



11. L- Amino Acid Oxidase, l-IIvduoxy Acid Oxidase 



Although its activity in tissue had been investigated by niuiiy workers 

 before and after Krebs'^--*'' classical studies, it was not until 1914 that 

 Stumpf and Green'^'* obtained a cell-free preparation of L-amino acid oxidase 

 from Proteus vulgaris. The following year, the first electrophoretically 

 homogeneous L-amino acid oxidase was prepared by Blanchard el nl.^^- '•"' 

 from rat kidnej^s. A distinguishing feature of this preparation was that 

 riboflavin monophosphate was the prosthetic group. Later, these workers^^ 

 showed that this enzyme was able to catalyze the oxidation of L-a-hydroxy 

 acids. The apparent specificity of the enzyme for the L-antipodes was at- 

 tested by the fact that L-lactic acid is completely oxidized, whereas dl- 

 lactic acid is only 50 % oxidized. 



Another water-soluble L-amino oxidase is found in snake venom. This 

 has been studied by Zeller and Maritz^- and Singer and Kearney*^ and 

 may be a flavoprotein. 



a. Preparalion 



Blanchard el al.^'^ started with a cold homogenate of 1.5 kg. of rat kidney 

 which was dewatered and dried with the aid of cold acetone. They used an 

 extensive series of extractions and precipitations from salt solutions, in- 

 cluding stepwise fractionations between 30 and GO % ammonium sulfate 

 saturations. 



b. Properties 



L- Amino acid oxidase is more difficult to extract from ground tissue than 

 D-amino acid oxidase. It is more rapidly denatured by organic solvents, is 

 inhibited by cyanide, and has only a small fraction as much activity as 

 D-amino acid oxidase in liver or kidney slices.*- 



The enzyme is electrophoretically homogeneous,^" but in the ultracen- 

 trifuge two components appeared. The lighter component (molecular 

 weight 138,000) contained 2 molecules of the riboflavin phosphate. The 

 heavier component (molecular weight 555,000), which seems to be an ag- 

 gregate of 4 molecules of the lighter component, had 8 molecules of flavin. 

 The flavin content was 0.66 %. The enzyme from rat kidney and liver cata- 



«8 P. K. Stumpf and D. E. Green, /. Biol. Chem. 153, 387 (1944). 



"M. Blanchard, D. E. Green, V. Xociti-Carroll, and S. Ratner, J. Biol. Chem. 



155, 421 (1944). 

 'o.M. Blanchard, D. E. Green, V. Xociti-Carroll, and S. Ratner, J. Biol. Chem. 



161, 583 (1945). 

 »' M. Blanchard, D. K. Green, V. Nociti-Carroll, and S. Ratner, J. Biol. Chem. 163, 



137 (1946). 

 " E. A. Zeller and \. Maritz, Helv. Chim. Aela 27, 1888 {V.)U); Helv. Physiol. Ada 3, 



048 (1945). 

 " T. P. Singer and E. B. Kearney, Federation Proc. 8, 251 (1949). 



