Specific Requirements for the Action of Deoxyribonuclease


THE mechanism of action of pancreatic deoxyribonuclease, now available in the crystalline state1,2, on highly polymerized deoxypentose nucleic acids is still obscure. The enzymatic attack is known to result in the formation of dialysable oligonucleotides and of a non-dialysable ‘core’ which, in the case of the nucleic acids from calf thymus3,4 and wheat germ5, is characterized by proportions of adenine, and to a lesser degree of thymine, greatly in excess of those encountered in the original substrate. Mononucleotides and inorganic phosphate are not found among the degradation products3,4, and this precludes the attribution to deoxyribonuclease of functions similar to those of phosphomonoesterases. It could be regarded as a phosphodiesterase of a closely circumscribed, as yet undefinable, specificity. A small number of acidic groups is, in fact, Liberated during the digestion6. That the attack of an enzyme the action of which consists in the depolymerization of a substance of high molecular weight, exhibiting no easily recognizable periodicity of constituent sequence, must follow an intricate pattern is clear: every break of the original molecule produces substrates that are new and different; the enzyme must deal with kaleidoscopic substrate changes.

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TAMM, C., CHARGAFF, E. Specific Requirements for the Action of Deoxyribonuclease. Nature 168, 916–917 (1951). https://doi.org/10.1038/168916a0

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