Enzymes in KEGG database are recorded with their enzyme commission (EC) number, which fully specifies the enzymatic transformations, and uses a topological classification scheme to categorise enzymes/enzymatic transformations into four levels. For example, from Figure , the EC number of enzyme MCR is 1. The binding between substrates and enzymes is a function of the secondary and tertiary structures of proteins, i.e. the physiochemical property of constituting amino acids to form the peptide chains of the proteins. We extracted genes which transcribe and translate into the protein of the enzymes from KEGG genes database for all recorded enzymes. KEGG genes database also gives the amino acid sequences of the specific gene. One enzyme usually links with multiple genes, varied from the cell organism (e.g. human serum albumin (hsa), bacterial, etc.), which originally hosts this enzyme. However, the amino acid sequences of the different genes are usually close. For example, for MCR -EC 1.2.1.75, two genes are reported: (1) mse: Msed_0709, and (2) sto: STK_21710, whilst both genes are linked with identical 357 amino acid sequences. For each enzyme, we only included one gene/amino acid sequence to include in the dataset. To minimise the biases on the selection from multiple amino acid options to affect the model results, the principles to select the gene/amino acid were: (1) to select the reported literature sources of the enzyme which were mostly cited, (2) to stick to one cell organism if possible -hsa. The selected gene names and amino acid sequences chosen for the model are given in Section 6 of ESI.