| dc.description.abstract | Theileria parva schizonts were cultured in bovine peripheral lymphocytes.
After schizogony, when the majority of the daughter cells were infected,
selective lysis of the lymphoblasts was effected with aerolysin. The optimum
concentration of aerolysin was determined using rabbit erythrocytes and was
found to be approximately 540 ug/ml for 2 x 108 erythrocytes. This
concentration of aerolysin was used throughout the study to lyse the infected
bovine lymphocytes in order to release the schizonts for biochemical studies.
To carry out enzyme assays the enzymes were released from the
parasites using 0.02 % (w/v) Triton-Xl 00 which disrupts the cell membranes.
Some glycolytic enzymes were assayed and all the following were
found to have activities greater than 20.0 nmoles/min/mg protein at 25°C:
hexokinase, glucosephosphate isomerase, phosphofructokinase, fructose 1,6-
diphosphate aldolase, phosphoglycerate kinase, enolase, pyruvate kinase and
lactate dehydrogenase. The glycerol kinase and a-glycerophosphate
dehydrogenase which are required during glycerol metabolism were found to
have very low activities which were less than 3.0 nmoles/rnin/mg protein. It
was proposed that the catabolism of glucose by the Theileria parva schizont
involves the Embden-Meyerhofpathway and that glycerol is hardly utilized as
substrate for energy production.
From the mean activity of glucose 6-phosphate dehydrogenase
which was found to be 3.8 nmoles/min/rng protein, it was proposed that the
pentose phosphate pathway exists in T parva schizonts.
Pyruvate carboxylase and glutamate pyruvate transaminase
activities were greater than 15.0 nmoles/minlmg protein. It was suggested that
there could be significant carboxylation of pyruvate to oxaloacetate and that
transamination of glutamate with pyruvate also occurs. a-Ketoglutarate is
formed via this transamination. It was also proposed that pyruvate carboxylase
plays an important role in further metabolism of pyruvate.
To determine how the a-ketoglutarate formed via the glutamate
pyruvate transaminase-catalysed reaction is used, the activity of glutamate
oxaloacetate transaminase was also determined and found to be 18.0
nmoles/minlmg protein. It was suggested that a-ketoglutarate in T .parva is
also transaminated with aspartate to form oxaloacetate.
The following Krebs cycle enzyme activities were less than 2.0
nmoles/minlmg protein and were considered insignificant: citrate synthase,
aconitase, NAD+-isocitrate dehydrogenase, NADP+-isocitrate dehydrogenase
and a-ketoglutarate dehydrogenase. It was proposed that the Krebs cycle is
incomplete in T parva schizont and that it does not contribute significantly
towards energy production.
The Krebs cycle enzymes found to have significant activities were:
malate dehydrogenase, succinate dehydrogenase and fumarase. Their activities
were more than 6.0 nmoles/minlmg protein. It was proposed that these
enzymes catalyse reactions involved in other pathways leading to formation of
oxaloacetate. | en |
