Conversion of 1,4-dihydroxy-2-naphthoate (DHNA) to demethylmenaquinone (DMK). Attaches octaprenylpyrophosphate, a membrane-bound 40-carbon side chain to DHNA. The conversion of DHNA to DMK proceeds in three stages: the removal of the carboxyl group of DHNA as CO(2), the attachment of the isoprenoid side chain, and a quinol-to-quinone oxidation, which is thought to be spontaneous. 1,4-dihydroxy-2-naphthoate + an all-trans-polyprenyl diphosphate + H(+) = a 2-demethylmenaquinol + CO2 + diphosphate Quinol/quinone metabolism; menaquinone biosynthesis; menaquinol from 1,4-dihydroxy-2-naphthoate: step 1/2. Belongs to the MenA family. Type 1 subfamily.