VITAMINS 341 



It is believed that the first two are converted to pyridoxal, which is 

 then phosj)horylated to form the real coenzyme, pyridoxalphosphate. 

 All forms are available commercially, but the coenzyme itself is still 

 $50/100 mg. Only pyridoxine is made on a sufficient synthetic scale 

 for use in vitamin supplements at $295/kg, of the hydrochloride. 



Function 



In so far as is known, only pyridoxalphosphate j^articipates in 

 metabolism. In this form vitamin Bg is both universally distributed 

 and involved in a variety of reactions. Many of these are important 

 in the metabolism of amino acids serving in decarboxylations, oxida- 

 tions, transaminations, racemizations, and syntheses, especially of tryp- 

 tophan. 



A complex and detailed mechanism of action has been worked oiU 

 for pyridoxalphosphate in most of its roles. Since modern theories of 

 advanced organic chemistry are fundamental to this outline, it is not 

 presented here. Reviews should be consulted for a full presentation. 



Requirements 



Daily reqiurements depend upon the intake of protein and amino 

 acids, especially tryptophan. The intestinal flora affects the supply. 

 Hence it is impossible to estimate reliably an allowance for man in 

 the absence of extensive dietary studies with human beings. Deficien- 

 cies may occur in conjunction with those of any of the other vitamins 

 already discussed. Rats require about 10 mg. per day, whereas chicks 

 need about 1.6 mg/lb. of feed. 



Vitamin B^ is usually associated in nature with the other members 

 of the B group, including niacin. It is relatively abundant in grains 

 and seeds, egg yolk, yeast, and meat. Corn is a good source in contrast 

 to its low nicotinamide content. 



Deficiency 



Natural uncomplicated deficiencies of vitamin Bp, arc imknown in 

 man. Experimental deficiencies in rats and pigs lead to loss of hair, 

 dermatitis, poor growth, loss of weight, anemias, and convulsions. 

 Degeneration of spinal and peripheral nerves occurs. Dairy cattle 

 sometimes develop similar symptoms spontaneously. Administration 

 of the vitamin reduces these disturbances quickly during early stages 

 of the disease. 



