## 3 Results
### Metabolic Pathways That Are Associated with the Top Scoring Enzyme Groups
It noteworthy that these top 100 scoring enzymes belong to the top three scoring enzyme groups (glycosases (3.2.1), CoA-transferases (2.8.3), and hydro-lyases (4.2.1)) identified by the EC-nomenclature-based G-S-M approach when applied to the CRC-associated metagenomic dataset. The top 100 scoring enzymes play roles in different pathways, such as starch and sucrose metabolism, biosynthesis of secondary metabolites, amino sugar and nucleotide sugar metabolism, galactose metabolism, N-Glycan biosynthesis, fructose and mannose metabolism, sphingolipid metabolism, and butanoate metabolism. The enzymes in the glycosidases (EC: 3.2.1) group take part in different metabolisms. For example, oligo-1,6-glucosidase (EC: 3.2.1.10) plays a role in galactose metabolism and starch and sucrose metabolism (as illustrated in Figure 11A,C). On the other hand, mannosyl-oligosaccharide glucosidase (EC: 3.2.1.106) and mannosyl-oligosaccharide 1,2-alpha-mannosidase (EC: 3.2.1.113) play a role in N-Glycan biosynthesis (as depicted in Figure 11D). Dextranase (EC: 3.2.1.11) plays a role in starch and sucrose metabolism (as shown in Figure 11A). In addition to that, many of the enzymes in the glycosidases (EC: 3.2.1) group have activity in sphingolipid metabolism (showcased in Figure 11B). In starch and sucrose metabolism (Figure 11A), the energy source of starch is converted to maltodextrin by isoamylase (EC: 3.2.1.68), alpha-amylase (EC: 3.2.1.1), beta-amylase (EC: 3.2.1.2), and glucan 1,4-alpha-maltohydrolase (EC: 3.2.1.133) enzymes. Later, maltose is converted to D-Glucose with the help of the maltase (EC: 3.2.1.20) enzyme. D-Glucose is synthesized to be used as an energy source. In sphingolipid metabolism (Figure 11B), beta-galactosidase (EC: 3.2.1.23), hexosaminidase (EC: 3.2.1.52), sialidase (EC: 3.2.1.18), and alpha-galactosidase (EC: 3.2.1.22) enzymes contribute to increase the amount of lactosyl-ceramide in the cell. The beta-galactosidase (EC: 3.2.1.23) enzyme converts Lactosyl-ceramide to Glucosyl-ceramide, which is converted to ceramide by the glucosylceramidase  
Figure 9: GO MF terms for the top 3 scoring enzymes that belong to the top 3 scoring enzyme groups, which were identified by the EC-nomenclature-based G-S-M model applied to the CRC-associated metagenomic dataset. GO hierarchy was obtained from the Quick-GO annotations provided by NCBI. enzyme (EC: 3.2.1.45). The amount of sphingosine is increased through the conversion of ceramide, glucosylsphingosine, and psychosine by ceramidase (EC: 3.5.1.23), glucosylc-ramidase (EC: 3.2.1.45), and galactosylcramidase (EC: 3.2.1.46), respectively (Figure 11B). Alpha-galactosidaseosidase (EC: 3.2.1.22), alpha-glucosidase (EC: 3.2.1.20), oligo-1,6-glucosidase (EC: 3.2.1.10), and saccharase (EC: 3.2.1.26) contribute to the production of d-Galactose, d-Glucose, and d-Fructose in galactose metabolism (Figure 11C). \(N\)-glycan biosynthesis begins in the endoplasmic reticulum (ER), where a precursor glycan is assembled and attached to nascent proteins. This glycan is then processed by glycosidases, including mannosyl-oligosaccharide glucosidase (EC: 3.2.1.106), mannosyl-oligosaccharide alpha-1, 3-glucosidase (EC: 3.2.1.207), endoplasmic reticulum Man9 GlcNAc2,1-alpha-mannosidase (EC: 3.2.1.209), and mannosyl-oligosaccharide 1,2-alpha-mannosidase (EC: 3.2.1.113). Further maturation and modification of N-glycans occur in the Golgi apparatus. (Figure 11D). The enzymes in hydro-lyases (EC: 4.2.1) and CoA-transferases (EC: 2.8.3) cordially play roles in many different metabolic pathways, such as styrene degradation, butanoate metabolism, carnitine metabolism, and the citric acid cycle (as shown in Figure 12). Nitrile hydratase (EC: 4.2.1.84) and lactoyl-CoA dehydatase (EC: 4.2.1.54) enzymes, which are part of the hydro-lyases group (EC: 4.2.1), have a role in the styrene degradation pathway. The metabolites from styrene degradation transform into pyruvate metabolism (as shown in Figure 12A).