Found it! Go to http://www.genome.jp/kegg-bin/get_htext?ko00001.keg and use the "download htext" link for a complete listing of all pathways/KO numbers!

There's an API, why not use it?

#!/bin/bash
echo "Downloading pathway list"
(curl -# http://rest.kegg.jp/list/pathway > ./pathway.list)
if [ $? -eq 0 ]; then
    for next in $(cut -f1 pathway.list); do
    (curl -# http://rest.kegg.jp/link/ko/$next > ./$next.ko)
    if [ $? -eq 0 ]; then
        echo "Retrieved $next ko map"   
    else
        echo "There was a problem in data retrieval"
        exit 1
    fi
    done
    exit 0
else 
    echo "There was a problem in data retrieval"
    exit 1
fi

The KEGG API page has a few ways to extract most formats of KEGG annotations. In your case, grabbing all the KO entries in a pathway would look like this:

/link/ko/map00010 or /link/ko/ko00010 will give you a list of all KO entries in pathway map00010 or ko00010

For r users, Dan Tenenbaum has a great r package for such a purpose. The method "keggLink" should be suitable for your purpose.

keggLink("ko","ko00010")

KEGG API link: http://www.genome.jp/kegg/rest/keggapi.html KEGGREST r package: https://www.bioconductor.org/packages/devel/bioc/manuals/KEGGREST/man/KEGGREST.pdf

In my case using the ko00001.keg file does not solve the problem at all because I have some "K numbers" which does not exist in this file.

Any idea where a suitable file with all the mappings is available?

Thanks!