KEGG Modules

For this post, I will explore a concept that I had trouble following in lecture: What is a a KO identifier? In the M. Kanehisa paper, the KEGG Orthology (KO) system is "a collection of manually de- fined ortholog groups (KO entries) for all proteins and functional RNAs that appear in the KEGG pathway maps". It became clear that the KO identifiers are used to map gene sequences to reactions & pathways. In one sense, they are a way of dealing the variation of different species to the reference pathways and reactions in KEGG. For example, some pathways may have variations when comparing reference pathways to humans vs. bacteria. KO identifiers also link information about the sequence of enzymes. In this way, enyzmes with similar sequences can be found quickly. I was also confused about the concept of a KEGG module. Reading this M. Kanehisa paper and getting understanding of what a KO identifier was also helped me understand that these KEGG modules were just groupings of sub-pathways, or KO's in a particular reaction sequence.