FUNCTION: PROVIDES THE PRECURSORS NECESSARY FOR DNA SYNTHESIS. * CATALYTIC ACTIVITY: 2'-deoxyribonucleoside diphosphate + oxidized thioredoxin + H2O = ribonucleoside diphosphate + reduced thioredoxin. * ENZYME REGULATION: UNDER COMPLEX ALLOSTERIC CONTROL MEDIATED BY THE BINDING OF DEOXYNUCLEOSIDE TRIPHOSPHATES AND ATP TO BINDING SITES ON THE M1 SUBUNIT. * PATHWAY: DNA replication pathway; first step. * SUBUNIT: HETERODIMER OF A LARGE (M1) AND A SMALL CHAIN (M2). * SUBCELLULAR LOCATION: Cytoplasmic. * DISEASE: RIBONUCLEOTIDE REDUCTASE IS THOUGHT TO MEDIATE THE PATHOGENESIS OF THE IMMUNODEFICIENCY OF ADENOSINE DEAMINASE OR PURINE NUCLEOSIDE PHOSPHORYLASE. THE DESOXYNUCLEOTIDES THAT ACCUMULATE IN THE LYMPHOID CELLS OF THESE PATIENTS ARE THOUGHT TO FEED-BACK INHIBIT RIBONUCLEOTIDE REDUCTASE, PREVENTING DNA REPLICATION AND CELL PROLIFERATION. * MISCELLANEOUS: TWO DISTINCT REGULATORY SITES HAVE BEEN DEFINED: THE SPECIFICITY SITE, WHICH CONTROLS SUBSTRATE SPECIFICITY, AND THE ACTIVITY SITE WHICH REGULATES OVERALL CATALYTIC ACTIVITY. A SUBSTRATE-BINDING CATALYTIC SITE, LOCATED ON M1, IS FORMED ONLY IN THE PRESENCE OF THE SECOND SUBUNIT M2. * MISCELLANEOUS: THE LEVEL OF THE ENZYME ACTIVITY IS CLOSELY CORRELATED WITH THE GROWTH RATE OF A CELL AND APPEARS TO VARY WITH THE CELL CYCLE. * SIMILARITY: BELONGS TO THE RIBONUCLEOSIDE DIPHOSPHATE REDUCTASE LARGE CHAIN FAMILY. |
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25-JAN-03
Last Update 13-Mar-03