title: Enzymes of deoxythymidine triphosphate biosynthesis in Neurospora crassa mitochondria.
abstract: Intact mitochondria of Neurospora crassa incorporate deoxythymidine 5'-monophosphate (dTMP) into deoxyribonucleic acid but not the label from (methyl-3H) deoxythymidine. Mitochondrial homogenates contain deoxythymidylate kinase (EC 2.7.4.9), deoxycytidylate aminohydrolase (dCMP deaminase) (EC 3.5.4.12), and thymidylate synthetase (EC 2.1.1b), but not thymidine kinase (EC 2.7.1.21) activity. dTMP kinase is loosely bound to the mitochondrial membrane and is solubilized by 0.4 M KCl in mitochondrial homogenates, the dCMP aminohydrolase deaminase) is bound to the inner membrane and is not solubilized by 0.4 M KCl. dTMP synthetase activity is found in the 2,000 times g particulate fractions by homogenization of mitochondria in 0.4 M KCl. The dCMP deaminase activity found in the particulate fraction of the inner membrane is efficiently regulated by the products of the pathway: deoxycytidine 5'-triphosphate activates whereas deoxythymidine 5'-triphosphate inhibits, as found for the soluble enzyme from other sources. These data indicate that mitochondria of N. crassa contain specific enzymes for the biosynthesis of deoxythymidine triphosphate.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000619:Aminohydrolases / Q000378:metabolism; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004247:DNA / Q000096:biosynthesis; D003854:Deoxyribonucleotides / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology*; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology* / Q000648:ultrastructure; D010770:Phosphotransferases / Q000378:metabolism; D011189:Potassium Chloride; D012995:Solubility; D013936:Thymidine / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D013940:Thymidylate Synthase / Q000378:metabolism; D013942:Thymine Nucleotides / Q000096:biosynthesis*
chemical_list: D003854:Deoxyribonucleotides; D013942:Thymine Nucleotides; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D004247:DNA; D003576:Electron Transport Complex IV; D013940:Thymidylate Synthase; D010770:Phosphotransferases; D013937:Thymidine Kinase; D000619:Aminohydrolases; D008274:Magnesium; D013936:Thymidine