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      Active-site- and substrate-specificity of Thermoanaerobium Tok6-B1 pullulanase.

      Plant, Adrian R.; Clemens, Robyn M.; Morgan, Hugh W.; Daniel, Roy M.
      Link
       www.biochemj.org
      Citation
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      Plant, A.R., Clemens, R.M., Morgan, H.W. & Daniel, R.M. (1987). Active-site- and substrate-specificity of Thermoanaerobium Tok6-B1 pullulanase. Biochemical Journal, 246(2), 537-541.
      Permanent Research Commons link: https://hdl.handle.net/10289/4536
      Abstract
      Thermoanaerobium Tok6-B1 pullulanase (EC 3.2.1.41) was active on alpha 1-6-glucosidic linkages of pullulan, amylopectin and glycogen and the alpha 1-4 linkages of amylose, amylopectin and glycogen but not of pullulan. Hydrolysis of short-chain-length malto-oligosaccharides (seven or fewer glucose residues) yielded maltose as product. Pullulan hydrolysis was pH-dependent and a plot of log(V/Km) versus pH implied a carboxy group with pKa 4.3 at the active site. Modification with 1-(3-dimethylaminopropyl)-3-ethylcarbodi-imide (EDAC) confirmed this view, and analysis of the order of reaction and inactivation kinetics suggested the presence of a single carboxy group at a catalytic centre of the active site. EDAC-mediated inhibition of pullulan alpha 1-6-bond hydrolysis was relieved by amylose or pullulan. Similarly both pullulan and amylose protected the activity directed at alpha 1-4 bonds of amylose from EDAC inhibition. When both amylose and pullulan were simultaneously present, the observed rate of product formation closely fitted a kinetic model in which both substrates were hydrolysed at the same active site.
      Date
      1987
      Type
      Journal Article
      Collections
      • Science and Engineering Papers [3077]
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