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COMPARATIVE STUDIES ON DIHYDROOROTATE DEHYDROGENASE FROM P. BERGHEI AND THE MOUSE RETICULOCYTE
Author(s) -
Gero Annette M,
Finney Kenneth G,
Bennett Julie C,
O'Sullivan William J
Publication year - 1981
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1981.41
Subject(s) - dihydroorotate dehydrogenase , reticulocyte , biology , biochemistry , enzyme , rna , gene
Summary Kinetic parameters on dihydroorotate dehydrogenase (DHO‐DHase) from the rodent malarial parasite, Plasmodium berghei , have been determined. This enzyme, the fourth in de novo pyrimidine biosynthesis, is particulate and is absent in the mature mammalian red cell. The K m of the substrate, dihydroorotate, was determined to be 23 μM and the K 1 values for a number of substrate analogues have been determined. The most potent inhibitor was dihydroazaorotate (K 1 , 3 μM). The product orotate was also a good inhibitor (K 1 , 5 μM) as were methylorotate (K 1 , 10 μM), 5‐azaorotate (K 1 , 20 μM) and other pyrimidine analogues. The activity of the enzyme was also affected by a number of respiratory chain inhibitors. As the P. berghei infection is accompanied by reticulocytosis, a comparative study of DHO‐DHase in mouse reticulocytes was also carried out. The general properties of the enzyme from these sources were similar to those of the parasite enzyme. However, significant differences in the response of the two enzymes to various inhibitors were observed and could provide a rational basis for the development of chemotherapeutic agents active against the parasite.