Über den Abbau der Oligonucleotide aus Thymo-nucleinsäure durch Darmfermente. Nucleinsäuren IV

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Abstract
Three enzymes were required to form nucleo-sides from a-thymonucleic acid; a polynucleotidase which split the acid to give oligonucleotides, and oligonucleoti-dase which acted on the oligonucleotides to form mono-nucleotides and a mononucleotidase which dephosphorylated the nucleotides. The enzyme prepns. used were prepared in a manner similar to that descr. previously (Hoppe-Seyler''s Zeitschr. physiol. Chem., 269: 169, 1941). The reaction mixtures usually contained 5 ml. desribotetranucleotide soln. (containing 8-10 mg. organically bound P), 3 ml. N NH3-NH4Cl buffer, 1 ml. M MgSO4 soln., and 5 ml. enzyme soln. The mixtures were incubated 53-1066 min. at 38[degree]. Samples were removed at intervals, the amt. of inorganically bound P detd. colorimetrically and the % splitting of the substrate calculated. Intestinal mucosa nucleotidase prepns. of varying degrees of purity showed the same activity towards mononucleotides but dephosphorylated desribotetranucleotide at different rates. This difference was due to the presence of the enzyme which split tetranucleotides to mononucleotides and which was removed during the purification of the mononucleotidase. This enzyme, for which the name desribooligonucleotidase was proposed, was not identical with desribopolynucleotidase from pancreas. Mononucleotidase prepns. dephosphorylated the tetranucleotide to give thymosine and adeninedesriboside. Thymosine- and adeno-sinephosphoric acid must be the nucleotides occupying the outer positions in desribotetranucleotide.

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