Conversion of 1,4-dihydroxy-2-naphthoate (DHNA) to demethylmenaquinone (DMK). Can use a variety of allylic isoprenyl diphosphates as substrates but has a requirement for at least three isoprene units. 1,4-dihydroxy-2-naphthoate + an all-trans-polyprenyl diphosphate + H(+) = a 2-demethylmenaquinol + CO2 + diphosphate Can also use Fe(2+) or Zn(2+), with lower efficiency. Activity is abolished by EDTA. Inhibited by Ro 48-8071, which is non-competitive with regard to DHNA and competitive with regard to the isoprenyldiphosphate substrate. Optimum pH is 8.5. Quinol/quinone metabolism; menaquinone biosynthesis; menaquinol from 1,4-dihydroxy-2-naphthoate: step 1/2. Essential, it cannot be deleted. Belongs to the MenA family. Type 1 subfamily.