From: Electrical energy storage with engineered biological systems
Cycle or pathway | Substrate | Product | ATP requirements | NAD(P)H | Number of substrate molecules | Number of each product | ATPs per substrate molecules | Key enzyme(s) | Specific activity of key enzyme(s) (μmol/min/mg protein) | Note | Reference |
---|---|---|---|---|---|---|---|---|---|---|---|
Naturally Evolved Under Aerobic Conditions | |||||||||||
Serine cycle | Formaldehyde (CH2O) + CO2, methanol (CH4O) + CO2, methane (CH4) + CO2 | Acetyl-CoA (C2H3O-CoA) | 2 | 2 | 1 + 1 | 1 | 1 | A. Serine hydroxymethyltransferase (SHMT) (EC 2.1.2.1) (e.g. Geobacillus stearothermophilus, 37°C, pH 7.4) | A. 5 | This cycle has been found in methane-assimilating microorganisms. | |
Ribulose monophosphate (RuMP) pathway- Entner–Doudoroff (EDD)-variant | Formaldehyde (CH2O), methanol (CH4O), methane (CH4) | 3-phosphoglycerate (C3H7O7P) | 2 | 1 | 3 | 1 | 0.6 | A. 6-phosphogluconate dehydratase (EC 4.2.1.12) | A. 0.033 | This pathway loses one carbon in the decarboxylation of pyruvate to acetyl-CoA. | Kalyuzhnaya et al. [172] |
B. 2-keto-3-deoxy-6-phosphogluconate aldolase (EC 4.1.2.14) (e.g. Methylomicrobium alcaliphilum, 28°C, pH 9) | B. 0.062 | ||||||||||
Artificially Evolved Under Aerobic Conditions | |||||||||||
Reductive glycine pathway (RGP or rGly) | Formate (HCO2-) + CO2 | Pyruvate (C3H3O3-) | 2 | 3 | 2 + 1 | 1 | 0.6 | A. Formate dehydrogenase (EC 1.17.1.9) (e.g. Mycobacterium vaccae, 30°C, pH 6.5) | A. 3.24 | This pathway is reversible and Yishai et al. believe this is the most efficient pathway, even though it needs an extra CO2. | |
B. Tetrahydrofolate (THF) dehydrogenase (EC 1.5.1.3) (e.g. Plasmodium falciparum, 25°C, pH 7) | B. 0.82 | ||||||||||
Methanol condensation cycle (MCC) | Formaldehyde (CH2O), methanol (CH4O), methane (CH4) | Acetyl-CoA (C2H3O-CoA) | 0 | 0 | 2 | 1 | 0 | A. Phosphoketolase (EC 4.1.2.9) (e.g. Clostridium acetobutylicum, 37°C, pH 6.5) | A. 2.01 | This pathway avoids the decarboxylation of pyruvate and achieves complete carbon conservation with the loss of only water. | Bogorad et al. [174] |
Formolase (dihydroxy-acetone variant) | Formate (HCO2-) | Glycerate 3P (C3H7O7P) | 5 | 2 | 1 | 1 | 5 | A. Formate-tetrahydrofolate ligase (FTL), (EC 6.3.4.3) (e.g. Homo sapiens) | A. 23 | The main barrier in this pathway is that formaldehyde as an intermediate limiting cell growth even at low concentrations. | |
Serine−threonine pathway, a variant of the methylotrophic serine pathway | Formate (HCO2-) + CO2 | Acetyl-CoA (C2H3O-CoA) | 10 | 4 | 1 + 1 | 1 | 5 | A. Serine hydroxymethyltransferase (EC 2.1.2.1) (e.g. Geobacillus stearothermophilus, 37°C, pH 7.4) | A. 5 | This pathway is considered to be a highly promising pathway. | Yishai et al. [173] |
B. Formate-tetrahydrofolate ligase (FTL), (EC 6.3.4.3) (e.g. Homo sapiens) | B. 23 | ||||||||||
Artificially evolved under anaerobic conditions | |||||||||||
pyruvate formatelyase- Phosphoketolase (PFL-PKT) | Formate (HCO2-) | Glycerate 3P (C3H7O7P) | 6 | 2 | 1 | 1 | 6 | A. Pyruvate formate-lyase (EC 2.3.1.54) (eg Streptococcus mutans) | A. 12 | A synthetic autocatalytic formate- assimilation cycle that is not dependent on fixation of inorganic carbon. | Bar-even et al. [127] |
B. Phosphoketolase (EC 4.1.2.9) (e.g. Lactobacillus pentosus) | B. 4.5 |