1. met is converted to homocysteine, then to aKB by CBS and CGL
2. met is degraded directly to aKB by MGL
In case when more than one patwhay present, use expression like: 1.2 (meaning 1 and 2 are present)
In case of missing genes (partial presence, use expression like: 1.x (meaning one gene is missing in variant 1).
For now we mark absence of either as "-1", although in fact the respective organisms likely have other pathways (yet unknown in many cases).
Rodionov DA, Vitreschak AG, Mironov AA, Gelfand MS. Comparative genomics of the methionine metabolism in Gram-positive bacteria: a variety of regulatory systems. Nucleic Acids Res. 2004 Jun 23;32(11):3340-53. PMID: 15215334