Table 2 Comparison of essential metabolic pathways among Cryptosporidium spp. and other common apicomplexan parasites^a

Carbohydrate and energy metabolism

Glycolysis

+

+

+

+

+

+

Methylcitrate cycle

-

-

-

-

-

+

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

-

-

-

-

-

+

UDP-Glc < - > UDP-Gal

+

+

+

+

-

+

GDP-Man < - > GDP-Fuc

-

-

-

-

+

+

UDP-Glc - > UDP-GlcA - > UDP-Xyl

+

+

+

+

-

-

Synthesis of mannitol from 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)

-

-

-

1 subunit

+

+

Oxidative phosphorylation (Complex IV)

-

-

-

-

+

+

F-ATPase

2 subunit

2 subunit

2 subunit

+

+

+

Alternative oxidase (AOX)

+

+

+

+

-

-

Glyoxalase metabolism producing D-lactate

-

-

-

-

+

+

Synthesis of isoprene (MEP/DOXP)

-

-

-

-

+

+

Synthesis of farnesyl/polyprenyl diphosphate

+

+

-

+

+

+

Nucleotide metabolism

Synthesis of purine rings de novo

-

-

-

-

-

-

IMP - > XMP - > GMP

+

+

+

-

+

+

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 branch-chain amino acids

-

-

-

-

-

+

Synthesis of tryptophan

+

+

+

-

-

-

Aromatic amino acid hydroxylases (AAAH)

-

-

-

-

-

+

Vitamin and others

Synthesis of ubiquinone (Coenzyme Q)

+

+

-

+

+

+

Synthesis of Fe-S cluster

+

+

+

+

+

+

Synthesis of heme

-

-

-

-

+

+

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 of lipoic acid in mitochondria

-

-

-

+

+

+

Synthesis of porphyrin/cytochrome proteins

-

-

-

-

+

+