Abstract
Mutant promastigotes of Leishmania donovani deficient in adenine phosphoribosyltransferase (AP-Rib transferase) have been isolated in medium containing 4-aminopyrazolopyrimidine. The generation of AP-Rib transferase-deficient mutants occurred in two discrete steps. In the first step, clones were isolated with 50% of wild-type levels of AP-Rib transferase activity. These cells were reselected, and colonies totally deficient in AP-Rib transferase were isolated. Wild-type and AP-Rib transferase-deficient cells contained equivalent amounts of other enzymes essential to adenine metabolism such as adenine deaminase and hypoxanthine-guanine phosphoribosyltransfer. Partially and totally AP-Rib transferase-deficient cells exhibited intermediate and complete resistance to cytotoxic adenine analogs, respectively. Nevertheless, wild-type and mutant cells could salvage adenine and utilize adenine as a purine source equally efficiently, suggesting that the adenine deaminase-hypoxanthine-guanine phosphoribosyl-transferase pathway plays an important role of promastigote adenine metabolism. Kinetic and thermal inactivation studies of purified AP-Rib transferase and isoelectric focusing of crude extracts from wild-type and partially AP-Rib transferase-deficient cells suggested that the latter cells possessed wild-type AP-Rib transferase activity at half the amount found in wild-type parental cells. These data suggest that L. donovani possesses two copies of the AP-Rib transferase structural gene and that these organisms might be diploid for the AP-Rib transferase locus.
Original language | English (US) |
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Pages (from-to) | 14617-14623 |
Number of pages | 7 |
Journal | Journal of Biological Chemistry |
Volume | 259 |
Issue number | 23 |
State | Published - 1984 |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology