Conversion of 1,4-dihydroxy-2-naphthoate (DHNA) to demethylmenaquinone (DMK). 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.