The mitochondrial DNA polymerase beta from Crithidia fasciculata has 5'-deoxyribose phosphate (dRP) lyase activity but is deficient in the release of dRP.
DNA polymerase beta (pol beta) has long been described as a nuclear enzyme involved in DNA repair. A pol beta from the trypanosomatid parasite Crithidia fasciculata, however, is the first example of a mitochondrial enzyme of this type. The mammalian nuclear enzyme functions not only as a nucleotidyl transferase but also has a dRP lyase activity that cleaves 5'-deoxyribose phosphate (dRP) groups from DNA, thus contributing to two consecutive steps of the base excision repair pathway. We find that the mitochondrial pol beta also has dRP lyase activity. Interestingly, the K(m) of this enzyme for a dRP-containing substrate is similar to that for the rat enzyme, but its k(cat) is very low. This difference is due to a deficiency of the mitochondrial enzyme in the release of dRP from the enzyme following its cleavage from the DNA.
Saxowsky
Tina T
TT
Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.
Matsumoto
Yoshihiro
Y
Englund
Paul T
PT
D000595:Amino Acid Sequence; D000818:Animals; D016831:Crithidia fasciculata / Q000201:enzymology*; D019951:DNA Polymerase beta / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008322:Mammals; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D019761:Phosphorus-Oxygen Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D011994:Recombinant Proteins; C423906:5'-deoxyribose phosphate lyase; D019951:DNA Polymerase beta; D019761:Phosphorus-Oxygen Lyases