This family includes two enzymes which are involved in menaquinone biosynthesis. One which catalyses the conversion of cyclic de-hypoxanthine futalosine to 1,4-dihydroxy-6-naphthoate, and one which may be involved in the conversion of chorismate to futalosine [1]. These enzymes comprise two domains with alpha/beta structures, a large domain and a small domain. A pocket between the two domains may form the active site, a conserved histidine located within this pocket could be the catalytic base [2].

1: An alternative menaquinone biosynthetic pathway operating in microorganisms. Hiratsuka T, Furihata K, Ishikawa J, Yamashita H, Itoh N, Seto H, Dairi T; Science. 2008;321:1670-1673. PMID:18801996

2: Crystal structure of MqnD (TTHA1568), a menaquinone biosynthetic enzyme from Thermus thermophilus HB8. Arai R, Murayama K, Uchikubo-Kamo T, Nishimoto M, Toyama M, Kuramitsu S, Terada T, Shirouzu M, Yokoyama S; J Struct Biol. 2009;168:575-581. PMID:19602440