VOL. 12 (1953) BIOSYNTHESIS OF NUCLEOSIDES AND NUCLEOTIDES 261 



uridyl-phospho-i -glucose (UDP Glucose) + (^^P) phospho-i-glucose ^ uridyl (^2?) 

 phospho-i-glucose + phospho-i-glucose. 



This reaction as well as the reactions with galactose-i-phosphate does not take place 

 in Zwischenferment preparations. 



Trucco^^ has found that ATP -\- UDP can act as "Co-Waldenase" in the conversion 

 of galactose-i-phosphate to glucose-i -phosphate in dialyzed S. fragilis extracts. The 

 catatytic effect of UTP which we have demonstrated is presumably a step reaction in 

 Trucco's system. In general the demonstration of such reactions shows that the so- 

 called "Co Waldenase" test is not specific for UDPGlucose or UDPGalactose if per- 

 formed in crude dialyzed extracts of 5. fragilis. The UDPGlucose pyrophosphorolytic 

 test with "Zwischenferment" andTPN seems at the present time to be the most specific 

 test for UDPGlucose. 



The occurrence of other uridyl phosphoglucosyl compounds 



i. "UDPX" from yeast; this component has most recently been identitied by 

 Leloir and his colleagues as uridyl phospho-i-(N-acetyl 2- amino) glucose^^. 



'ii. "UDPX" compounds from Staphylococcus aureus metabolizing in the presence 

 of penicillin. '^^ Park^° has identified these compounds. 



Compound i : (N-acetyl, 2 amino) uronic acid. 



Compound 2 : Same type with extra incorporated alanine. 



Compound 3 : same type with extra incorporated peptide (containing d and l amino 

 acids) . 



iii. Uridyl phospho-i-glucuronic acid^^ 



Park and Johnson's discovery of the effect of penicillin on the accumulation of 

 uridine diphosphoglycosyl compounds of type ii poses the problem whether this anti- 

 biotic exerts a strong inhibition on a step enzyme of the uridyl transferase type. If about 

 0.5 Oxford unit of penicillin is added to a growing culture of staphylococci cell division 

 stops but expansion of the cells continues for another % to i hour during which time the 

 normal amount of "UDPX" is increased more than fifty fold. This accumulation of 

 uridine nucleotides seems to be at the expense of the formation of ribonucleic acid (see 

 next section). The recent observations that a uridine nucleotide which seems to have a 

 yS-phospho-i-glucuronic acid as the P-glycosyl component and works as a coenzyme 

 for the glucuronide synthesis^^ has already been discussed briefly. In this case there is 

 reason to believe that the exchange fission may take place at the glycosyl linkage. One 

 cannot help thinking that polysaccharides of a type like hyaluronic acid may serve as 

 glycosyl donors for UDP thus giving rise to the formation of UDPGluronic acid and 

 UDPX substances such as these classified under i and ii. 



Biosynthesis of nucleic acid linkages. It has in general been found that labelled 

 purines and pyrimidines if incorporated into nucleic acids are rapidly incorporated 

 into the 5-nucleotides of the corresponding N-bases. Administration of labelled adenine 

 to a perfused liver or to liver homogenates appears within a few minutes after the addi- 

 tion of the purine in 5-adenylic acid, ADP, and ATP*"-*!. In sea urchin embryos ^^C 

 adenine is incorporated rapidly into the 5-nucleotides and into deoxyribonucleic acid 

 and slowly into ribonucleic acid^^. Labelled orotic acid, which seems to be the only free 

 pyrimidine to be incorporated into the nucleic acids of the rat organism^^, appears first 

 in 5-uridylic acid nucleotides^^. Correspondingly, in micro-organisms capable of using 



References p. 26JI264. 



