Enzymatic Characterization of Acid Phosphatase in the Logarithmic and Stationary Phase of Leishmania major Promastigotes

Background: Leishmania is a protozoa of trypanosomatidae family that leads to a group of disease called leishmaniasis. The pathogenesis of parasite changes during promastigotes growth and proliferation. Proliferation of promastigotes includes two stages: logarithmic, and stationary. The parasite is noninfective at logarithmic stage while is infective during the stationary stage. Acid phosphatase (ACP) is one of the factors that supposed to play a role in preservation and survival of the parasites inside the vertebrate host body cells. Objectives: In the present study, ACP enzyme characteristics and its activity during logarithmic and stationary phases of Leishmania major were compared. Materials and Methods: The growth curve of L. major (MRHO/IR/75/ER) was plotted by daily counting cultivated parasites and promastigotes of each stage were collected separately. Frozen promastigotes of each stage were homogenized with sodium acetate and Triton-X-100 and ACP was measured by calorimetric assay. Results: Parasites at logarithmic and stationary phase were collected respectively in the fourth and seventh days. The rate of ACP activity was determined to be 1.18 ± 0.01 in stationary and 0.9 ± 0.03 ?M/min/mg protein in logarithmic phases. Moreover, maximum speed of phosphatase enzyme (Vmax) was 98.04 ± 0.96 in stationary phases and 75.76 ± 0.57 in logarithmic. In addition, Michaelis-Menten constant (km) in logarithmic and stationary phase was determined at 142.93 ± 4.08 and 106.39 ± 1.14 ?M, respectively (P < 0.05). Conclusions: In logarithmic phase, km of ACP was 28% higher and the rate of ACP activity and Vmax were 23% lower than that of stationary phase. Changes in the specifications of ACP might be one of the important factors for parasites to attack the macrophages and these variations.