This subgroup contains the triphosphate tunnel metalloenzyme (TTM) from Clostridium thermocellum (CthTTM) and similar proteins. These are found primarily in bacteria. CthTTM is a metal dependent tripolyphosphatase, nucleoside triphosphatase, and nucleoside tetraphosphatase. It hydrolyzes the beta-gamma phosphoanhydride linkage of triphosphate-containing substrates including tripolyphosphate, nucleoside triphosphates and nucleoside tetraphosphates. These substrates are hydrolyzed, releasing Pi. Mg++ or Mn++ are required for the enzyme's activity. CthTTM appears to have no adenylate cyclase activity. This subgroup consists chiefly of bacterial sequences. These enzymes are members of the CYTH-like (also known as triphosphate tunnel metalloenzyme (TTM)-like) superfamily, which have a unique active site located within an eight-stranded beta barrel.
Comment:Based on similarity to Clostridium thermocellum TTM, where these residues have been shown by mutation analysis to be important for tripolyphosphatase and ATPase activity.
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