Content area
Full text
Introduction
During the intraerythrocyte development stage, Babesia undergoes maturation and replication, resulting in parasitemia, which is the main pathology of babesiosis (Lobo et al. 2012). This rapid development necessitates a constant supply of nutrients, primarily glucose, to fulfill the parasite's energy needs (Beri et al. 2023; Ohmori et al. 2004). In apicomplexan parasites, the majority of glucose is metabolized into pyruvate, which is then reduced to lactate and expelled from the parasite. Although Babesia possesses all the genes necessary for the tricarboxylic acid (TCA) cycle and most of those required for electron transport chain (ETC) enzymes (Brayton et al. 2007; Liu et al. 2023; Singh et al. 2023), it relies predominantly on cytoplasmic glycolysis during the erythrocyte stage of development. Mitochondrial oxidative phosphorylation plays a minimal role in ATP synthesis in Babesia at this stage.
Energy acquisition and metabolism are critical for the survival and proliferation of all living organisms, and glucose metabolism represents the primary pathway through which life forms obtain energy (Mulukutla et al. 2016). The major pathways of ATP production in most organisms include glycolysis, the TCA cycle, and β-oxidation (Fernie et al. 2004). Glycolysis involves the breakdown of six-carbon glucose molecules into two molecules of phosphoenolpyruvate (PEP) through a nine-step enzymatic process, ending with substrate-level phosphorylation catalyzed by pyruvate kinase (Romano and Conway 1996). This results in the production of two three-carbon pyruvate molecules, generating two molecules of ATP to fuel the energy needs of living organisms (Kresge et al. 2005). The fate of pyruvate varies among species and depends on oxygen availability. Under aerobic conditions, pyruvate is transported into the mitochondria, where it undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex to produce acetyl-CoA (DeColli et al. 2018). Acetyl-CoA then combines with OOA—a product of PEP—to initiate the TCA cycle and oxidative phosphorylation, ultimately yielding CO2, H2O, and ATP to energize the organism (Arnold and Finley 2023). OOA, a crucial reactant in the TCA cycle, also serves as a significant source of malate, aspartate, and other substances, playing a vital role in the organism's material and energy metabolism.
Phosphoenolpyruvate carboxylase (PEPC) is a cytoplasmic enzyme present in a wide range of organisms, including plants, green algae, cyanobacteria, bacteria, archaea and protozoa (Izui et al. 2004; Storm...