670 



THE BIOCHEMISTRY OF B VITAMINS 



relatively high concentrations, which suggests that the phosphate group 

 facilitates combination of the coenzyme with the apoenzyme. 



Since a large number of compounds analogous to riboflavin were pre- 

 pared in the final synthetic approach to the structure of the vitamin 

 and were tested for activity in replacing the vitamin in the nutrition of 



a The activities relative to that of riboflavin are calculated from data of each reference. Inactivity under 

 the testing conditions is indicated by 0. Upper limits and in one instance the lower limit of activity are 

 indicated where data are not available for accurate estimate. 



b Inhibitory to growth. 22 This compound was reported in earlier work to have slight activity 13 ' I7 - 21 but 

 an Amadori rearrangement appears to have occurred during synthesis resulting in contamination of the 

 sample with riboflavin. 



c Maximum growth not obtained at any concentration. 



d Slightly active. 20 y per day kept the animals alive without much growth, but animals receiving 10 y 

 per day died in 2 to 5 weeks. 



• Maximum growth obtained with the analogue at any concentration reaches only the per cent indicated 

 in brackets of the maximum response to riboflavin. 



t Analogue inactive alone but enhances the response of the organism to riboflavin. 



o Data from separate experiments not strictly comparable on a quantitative basis. Per cent indicated 

 represents the relative oxygen consumption in the presence of comparable quantities of analogue unless 

 otherwise indicated. 



* Considered inactive; however, slight activities of enzyme preparations in absence of added analogue 

 do not permit accurate estimates of low activities. 



' Relative oxygen consumption obtained with 30 y riboflavin-5'-phosphate compared with 150 y ribo- 

 flavin. As little as 2.5 y riboflavin-5'-phosphate is essentially as active as 30 y in this system. 

 i Calculated on basis of activity (70%) in comparison to riboflavin-5'-phosphate. 33 



rats, the specificity of the structure for vitamin B 2 activity has been 

 extensively studied by the time proof of structure of the vitamin was 

 achieved. The activities of certain analogues in replacing riboflavin in 

 the nutrition of rats and certain microorganisms are indicated in Table 

 38. 



Many compounds analogous to riboflavin were also tested for activity 

 as a coenzyme of the yellow coenzyme. Oxygen uptake and methylene 

 blue decolorization were determined for the test substances when glucose- 



