Table 2.

Comparison of some essential metabolic pathways among common apicomplexan parasites^a

Category	Metabolic pathway	Cpar	Pfal	Bbov	Tgon	Eten	Ccay
Carbohydrate and energy metabolism	Glycolysis	+	+	+	+	+	+
	Degradation of propionyl-CoA into pyruvate and succinate	-	-	-	+	-	+
	TCA cycle	-	+	+	+	+	+
	Pentose phosphate pathway	-	+	+	+	+	+
	Shikimate biosynthesis	-	+	-	+	+	+
	Folate biosynthesis	-	+	-	+	+	+
	Synthesis of tetrahydrobiopterin/dihydrobiopterin/molybdopterin	-	-	-	+	-	-
	Galactose metabolism	-	-	-	+	+	+
	Synthesis of starch	+	-	-	+	+	+
	Synthesis of trehalose	+	-	+	+	+	+
	Synthesis of 1,3-beta-glucan	-	-	-	+	+	+
	Conversion between UDP-Glc and UDP-Gal	+	-	-	+	+	+
	Conversion between GDP-Man and GDP-Fuc	-	+	-	+	+	+
	Conversion of UDP-Glc to UDP-GlcA then to UDP-Xyl	+	-	-	-	-	-
	Synthesis of mannitol from mannose or fructose	+	-	-	-	+	+
	Fatty acid biosynthesis in cytosol (FAS I)	+	-	-	+	+	+
	Fatty acid biosynthesis in apicoplast (FAS II)	-	+	-	+	+	+
	Fatty acid degradation	-	-	-	+	+	+
	Oxidative phosphorylation (NADH dehydrogenase)	+	+	+	+	+	+
	Oxidative phosphorylation (Complex II)	-	+	+	+	+	+
	Oxidative phosphorylation (Complex III)	-	+	+	+	+	+
	Oxidative phosphorylation (Complex IV)	-	+	+	+	+	+
	F-ATPase	2 subunits	+	+	+	+	+
	V-ATPase	+	+	+	+	+	+
	Glyoxalase metabolism producing D-lactate	-	+	+	+	+	+
	Synthesis of isoprene (MEP/DOXP)	-	+	+	+	+	+
Nucleotide metabolism	Synthesis of purine rings de novo	-	-	-	-	-	-
	Synthesis of pyrimidine de novo	-	+	+	+	+	+
Amino acid metabolism	Synthesis of alanine from pyruvate	-	-	-	+	+	+
	Synthesis of glutamate from nitrite/nitrate	-	+	+	+	+	+
	Conversion from glutamate to glutamine	+	+	-	+	+	-
	Synthesis of aspartate from oxaloacetate and glutamate	-	+	+	+	+	+
	Conversion from aspartate to asparagine	+	+	-	+	+	+
	Conversion from glutamate to proline	+	-	-	+	+	+
	Synthesis of serine from glycerate/glycerol phosphate	-	-	-	+	+	+
	Conversion from serine to cysteine	-	-	-	+	+	+
	Conversion from serine to glycine	+	+	+	+	+	+
	Recycle homocysteine into methionine	-	+	-	+	-	-
	Synthesis of lysine from aspartate	-	-	-	+	-	-
	Synthesis of threonine from aspartate	-	-	-	+	-	-
	Synthesis of ornithine from arginine	-	+	-	-	-	-
	Synthesis of ornithine from proline	-	+	-	+	+	+
	Synthesis of polyamine from ornithine	-	+	-	-	-	-
	Polyamine pathway backward	+	-	-	+	+	+
	Degradation of leucine to acetyl-CoA	-	-	-	+	-	-
	Degradation of isoleucine/valine	-	-	-	+	+	+
	Aromatic amino acid hydroxylases (AAAH)	-	-	-	+	-	-
Vitamin and others	Synthesis of thiamine (vitamin B1)	-	+	-	-	-	-
	Conversion from thiamine to thiamine pyrophosphate (TPP)	-	+	-	+	-	+
	Synthesis of FMN/FAD from riboflavin	-	+	+	+	+	+
	Synthesis of pyridoxal phosphate (vitamin B6) de novo	-	+	-	+	-	-
	Synthesis of NAD(P) + de novo from nicotinate/nicotinamide	-	+	-	+	+	+
	Synthesis of pantothenate from valine	-	-	-	+	+	+
	Synthesis of CoA from pantothenate	+	+	+	+	+	+
	Synthesis of lipoic acid de novo in apicoplast	-	+	-	+	+	+
	Salvage lipoic acid in mitochondria	-	+	+	+	-	+
	Synthesis of porphyrin/cytochrome proteins	-	+	-	+	+	+

^aPlus symbol denotes that the essential enzymes for pathways were identified, whereas minus symbol denotes that the essential enzymes for pathways were absent. Only 2 subunits of the F-type ATPase are present in Cryptosporidium parvum. Abbreviation: Cryptosporidium parvum (Cpar); Plasmodium falciparum (Pfal); Babesia bovis (Bbov); Toxoplasma gondii (Tgon); Eimeria tenella (Eten); Cyclospora cayetanensis (Ccay)