Deoxyribosyl transfer

Deoxyribosyl Transfer via Free Deoxyribose 1-Phosphate ( Coupled Deoxyribosyl Transfer)... 

Deoxyribose 1-phosphate, derived from initial phosphorolysis of deoxyribonucleoside BidR, is utilized to form the new nucleoside B2dR, the net result (3) being deoxyribosyl transfer. This sequence is phosphate-de-pendent. 

In purine-purine deoxyribosyl transfer, a single enzyme, purine nucleoside phosphorylase (see Chapter 10), participates in both reactions (1) and (2). For example, the purified enzyme catalyzes the following reaction (16) ... 

Purine-pyrimidine deoxyribosyl transfer reactions result when reactions (1) and (2) are catalyzed by the joint actions of purine nucleoside phosphorylase and thymidine phosphorylase, that is, when the activities of these enzymes are coupled. For example, the following reaction is catalyzed by extracts of human leukocytes (18) ... 

In addition to participation in the deoxyribosyl transfer reactions described above, in which free deoxyribose 1-phosphate is formed as an intermediate, thymidine phosphorylase also catalyzes deoxyribosyl transfers involving thymine and uracil in which deoxyribosyl phosphate is an intermediate but is enzyme-bound (18-20). Such transfers require non-stoichiometric amounts of phosphate (19). The reaction mechanisms of uridine phosphorylase and purine nucleoside phosphorylase are not of this type and, accordingly, direct deoxyribosyl transfers occur only between substrates for thymidine phosphorylase, as exemplified by reaction (5) above and the following (15) (the asterisk indicates C-labeling) ... 

Many LactobaciUus species have an absolute growth requirement for a purine, a pyrimidine, and a single deoxyribonudeoside of any sort because the entire complement of cellular deoxyribonucleotides is derived from these materials, there is an evident requirement for the capability of transferring the deoxyribosyl function between bases in these cells. However, in lactobacilli deoxyribosyl transfer is not accomplished by the phosphorylase mechanisms outlined above in this connection it may be noted that lactobacilli are devoid of thymidine phosphorylase (4). A specific enzyme activity, intermediate formation of deoxyribose 1-phosphate, is readily reversible, and takes place in the absence of inorganic phosphate ... 

Extracts of certain bacteria requiring 2-deoxyribonucleosides, namely, Lactobacillus helveticus, Lactobacillus delbriickii, and Thermobacterium acidophilus R 26, catalyze the transfer of the 2-deoxy-D-ribosyl group from one purine or pyrimidine to another. " 2-Deoxyribosyl -uracil, thy-... 

All tested enzymatic (microbial ribosylnucleotide transferase) methods for the transfer of the ribosyl and 2-deoxyribosyl moiety to the alkaloid molecule (agroclavine) failed (e.g.[ 35]), presumably due to the very narrow specificity of the particular enzymes for certain aglycone molecules. 

Purine nucleoside phosphorylase and thymidine phosphorylase have been shown to catalyze transfer of the deoxyribosyl group from one base to another by reaction sequences that involve the intermediate formation of free deoxyribose 1-phosphate by the following mechanism ... 

Direct Transfer of Deoxyribosyl Groups by Thymidine Phosphorylase... 

Thymidine phosphorylases of both animal celts and E. coli catalyze this direct transfer of deoxyribosyl groups between thymine and uracil. 

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