Members of this family are found in all the three major phyla of life: archaebacteria, eubacteria, and eukaryotes. In Bacillus subtilis, TENA is one of a number of proteins that enhance the expression of extracellular enzymes, such as alkaline protease, neutral protease and levansucrase [1]. The THI-4 protein, which is involved in thiamine biosynthesis, is also a member of this family. The C-terminal part of these proteins consistently show significant sequence similarity to TENA proteins. This similarity was first noted with the Neurospora crassa THI-4 [2]. This family includes bacterial coenzyme PQQ synthesis protein C or PQQC proteins. Pyrroloquinoline quinone (PQQ) is the prosthetic group of several bacterial enzymes,including methanol dehydrogenase of methylotrophs and the glucose dehydrogenase of a number of bacteria [3]. PQQC has been found to be required in the synthesis of PQQ but its function is unclear. The exact molecular function of members of this family is uncertain.

1: Cloning and characterization of a pair of novel genes that regulate production of extracellular enzymes in Bacillus subtilis. Pang AS, Nathoo S, Wong SL; J Bacteriol 1991;173:46-54. PMID:1898926

2: Molecular cloning of thi-4, a gene necessary for the biosynthesis of thiamine in Neurospora crassa. Akiyama M, Nakashima H; Curr Genet 1996;30:62-67. PMID:8662211

3: PqqC/D, which converts a biosynthetic intermediate to pyrroloquinoline quinone. Toyama H, Fukumoto H, Saeki M, Matsushita K, Adachi O, Lidstrom ME; Biochem Biophys Res Commun 2002;299:268-272. PMID:12437981