Table 2. The 25 most abundant COGs of the protein core detected in human intestinal samples.
| COG group | Definition | COG functional category | MS/MS Spectra [%]* |
| COG0334 | Glutamate dehydrogenase/leucine dehydrogenase | E | 14.3 |
| COG1866 | Phosphoenolpyruvate carboxykinase (ATP) | C | 6.6 |
| COG1653 | ABC-type sugar transport system, periplasmic component | G | 5.2 |
| COG2115 | Xylose isomerase | G | 4.7 |
| COG0057 | Glyceraldehyde-3-phosphate dehydrogenase/erythrose-4-phosphate dehydrogenase | G | 4.1 |
| COG0176 | Transaldolase | G | 3.5 |
| COG0574 | Phosphoenolpyruvate synthase/pyruvate phosphate dikinase | G | 3.5 |
| COG0183 | Acetyl-CoA acetyltransferase | I | 3.3 |
| COG0148 | Enolase | G | 2.0 |
| COG3957 | Phosphoketolase | G | 2.7 |
| COG0126 | 3-phosphoglycerate kinase | G | 2.5 |
| COG1882 | Pyruvate-formate lyase | C | 2.2 |
| COG0166 | Glucose-6-phosphate isomerase | G | 2.0 |
| COG2160 | L-arabinose isomerase | G | 2.0 |
| COG0174 | Glutamine synthetase | E | 1.9 |
| COG0021 | Transketolase | G | 1.6 |
| COG0059 | Ketol-acid reductoisomerase | EH | 1.2 |
| COG0480 | Translation elongation factors (GTPases) | J | 1.2 |
| COG1454 | Alcohol dehydrogenase, class IV | C | 1.2 |
| COG0282 | Acetate kinase | C | 1.2 |
| COG1250 | 3-hydroxyacyl-CoA dehydrogenase | I | 1.1 |
| COG2407 | L-fucose isomerase and related proteins | G | 1.1 |
| COG1904 | Glucuronate isomerase | G | 1.0 |
| COG0822 | NifU homolog involved in Fe-S cluster formation | C | 1.0 |
| COG0459 | Chaperonin GroEL (HSP60 family) | O | 0.9 |
*contribution in percent of specific COG group to the total amount of identified spectra in the core metaproteome.
COG functional categories: C Energy production and conversion; E Amino acid transport and metabolism; G Carbohydrate transport and metabolism; H Coenzyme transport and metabolism; I Lipid transport and metabolism; J Translation, ribosomal structure and biogenesis; O Posttranslational modification, protein turnover, chaperones.