Recently we submitted a manuscript with some results of RNAseq. I used Gene Ontology and KEGG to do enrichment analysis for biological processes and pathways. Somehow one reviewer who might not be familiar with enrichment analysis asked why we linked some genes with certain biological processes. He/she asked us to put references to let readers know why these  genes are associated with mentioned biological processes and pathways. I initially thought this could be done and later I felt this is not necessary. First of all, all the gene assignments are done by GO or KEGG, not us. Some gene assignments have tens to hundreds of references based on GO or KEGG's database. We have totally around 50 GO biological processes and KEGG pathways in the paper and even putting all these gene level references into a supplemental table is too much. I've used GO and KEGG many times in various papers but that was my first time seeing this kind of comment. Is there a reasonable and polite way to address this? Thanks.