Temperature and metabolism in Leishmania: II. Aldolase in L. adleri, L. donovani, L. mexicana, and L. tarentolae

Abstract

Leptomonads of Leishmania adleri, L. donovani, L. mexicana, and L. tarentolae were grown in a blood-agar-Locke's overlay medium, harvested by centrifugation, homogenized in a mortar with quartz abrasive, and examined for fructose 1,6-diphosphate aldolase activity using colorimetric determinations incorporating 2,4-dinitrophenylhydrazine. Effects of elevated temperature, pH, enzyme concentration, substrate concentration, and reaction time were employed to characterize the enzymes partially, and these results were used for the comparative evaluation of the four species studied. Present findings are consistant with the accepted classification of the genus, which places L. adleri (the only species of Leishmania known which is capable of parasitizing both lizards and mammals) between the relatively primitive obligate lizard parasite, L. tarentolae, and the relatively specialized obligate mammal parasites, L. donovani and L. mexicana. The investigations revealed a number of significant differences among the aldolases of the four species. Leishmania adleri and L. tarentolae have an aldolase temperature optimum of 45 °C while the temperature optimum of the aldolase of L. donovani and L. mexicana is 32 °C. The K m values for the aldolases of L. adleri and L. tarentolae are 0.6 and 0.2 × 10 −3, respectively, which indicates they have a greater substrate affinity than the aldolases of L. donovani ( K m 1.2 × 10 −3) or L. mexicana ( K m 1.1 × 10 −3). The specific activity of L. tarentolae aldolase is considerably higher than those exhibited by the other three species. All of the data were in general agreement with previously published reports of aldolases from a variety of sources and were in close agreement with certain aspects of the aldolases (i.e., optimum temperature and K m values) of their vertebrate hosts. This study has extended to the enzyme-level the investigation of Leishmania species differences which are, in part, associated with temperature.