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Kanehisa Lab
KEGG in Keg

KEGG Syntax – KO Composition

Syntax Genome alignment KO composition Synteny analysis Taxonomy analysis

KO Composition

In the genome alignment tool the genome is characterized by the sequence of KOs and the similarity of genomes is obtained by comparing KO sequences. Here the genome is characterized by the composition of KOs and a simple measure of genome similarity is introduced to rapidly identify similar genomes and taxonomic groups. Two types of similarity measures are defined as shown below:
similarity = match / (num1 + num2 - match)
similarity1 = match / num1
where
num1 = number of distinct KOs in genome 1
num2 = number of distinct KOs in genome 2
match = number of matching KOs in genomes 1 and 2
The second type may represent whether and how a shorter genome is embedded in a longer genome.

Search genomes with similar KO compositions
Enter organism code or vtax number
Genome:   		     Threshold similarity: %
Genome examples: hsa eco mge 2681611 (Lambda phage)

VOG Composition

Since the KO assignment rate is very low for viral proteins, computationally generated VOGs may be used to measure similarity among viruses. Here the 30% level VOG (VOG30) is used to search against viruses and cellular organisms.

Search genomes with similar VOG compositions
Enter vtax number
Genome:   		     Threshold similarity: %
Genome examples: 2697049 (Coronavirus) 2681611 (Lambda phage) 212035 (Mimivirus)
Last updated: January 1, 2026