title: A putative adenosine kinase family protein possesses adenosine diphosphatase activity.
abstract: Adenosine kinase is a potential target for development of new types of drugs. The COG1839 family has been defined as "adenosine-specific kinase" family based on structural analysis and the adenosine-binding ability of a family member, PAE2307. However, there has been no experimental evidence with regard to the enzymatic function of this protein family. Here we measured the enzymatic activity of TTHA1091, a COG1839 family protein from Thermus thermophilus HB8. The phosphorylation of adenosine by TTHA1091 was undetectable when ATP or ADP were used as phosphate donor. However, the degradation of ADP to AMP was detected, indicating that this protein possessed adenosine diphosphatase (ADPase) activity. The (ADPase) activity was inhibited by divalent cations and was specific to ADP and CDP. Thus, this study provides the first experimental evidence for the enzymatic function of the "adenosine-specific kinase" family and suggests a need to reexamine its functional annotation.
authors.affiliation: a Graduate School of Frontier Biosciences , Osaka University , Suita , Osaka , Japan.|b Research Center for Materials Science , Nagoya University , Nagoya, Aichi , Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Tomoike
authors.affiliation: c Department of Biological Sciences , Graduate School of Science, Osaka University , Toyonaka , Osaka , Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tsunetou
authors.affiliation: c Department of Biological Sciences , Graduate School of Science, Osaka University , Toyonaka , Osaka , Japan.
authors.forename: Kwang
authors.initials: K
authors.lastname: Kim
authors.affiliation: c Department of Biological Sciences , Graduate School of Science, Osaka University , Toyonaka , Osaka , Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Nakagawa
authors.affiliation: a Graduate School of Frontier Biosciences , Osaka University , Suita , Osaka , Japan.|c Department of Biological Sciences , Graduate School of Science, Osaka University , Toyonaka , Osaka , Japan.
authors.forename: Seiki
authors.initials: S
authors.lastname: Kuramitsu
authors.affiliation: c Department of Biological Sciences , Graduate School of Science, Osaka University , Toyonaka , Osaka , Japan.|d Graduate School of Science , Osaka City University , Osaka , Japan.
authors.forename: Ryoji
authors.initials: R
authors.lastname: Masui
keywords: COG1839; adenosine diphosphatase; adenosine kinase; annotation