550 



A. P. Nygaard 



in Fig. 5. The curves were similar except for the drop in rate on the alkaline 

 side. 



The most active preparation of LDH II had relative activities (see earlier) 

 of 1 : 1 : 1 and turnover number 15,000 moles of cytochrome c reduced/min/ 

 mole of flavin or haem. The turnover number of a preparation of LDH III 



/ 



Fig. 5. The rate of the reduction of ferricyanide (5 x 10-^ m) by LDH II and III 

 as a function of pH (oL-lactate, 002 m). 



O o o LDH II 



AAA LDH III 



Buffers used: phosphate /< 008 at pH 7-7 and below; glycylglycine, 

 005 M, from pH 7-6 to 8-6; glycine, 005 m, from pH 8-6 to 9-7. 

 Change of buffer at pH 8-6 and 7-7 did not affect the activity. 



Ordinate: arbitrary velocity units. 



with cytochrome c in phosphate /^O-Ol, pH 7-1, was 6,000 //moles of cyto- 

 chrome c reduced/min/mole of flavin. The relative activities of LDH III 

 varied from preparation to preparation. The reduction of ferricyanide and 

 indophenol was usually less than 0-2 times that of cytochrome c. 



LDH II was specific for L-lactic acid, whereas LDH 111 was specific for 

 D-lactic acid. 



DISCUSSION 

 In a recent note Labeyrie, Slonimski and Naslin (1959) reported that lactate 

 dehydrogenase of anaerobic yeast was specific for D-lactate. This enzyme had 

 previously been shown not to reduce cytochrome c (Lindenmayer and Smith, 

 1957; Slonimski and Tysarowski, 1958; Boeri and Cutolo, 1958). Slonimski 

 and Tysarowski (1958) and Labeyrie et al. (1959) proposed that anaerobic 



