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Mapping of the Active Sites of Transglutaminases

Gross, Michael ; Folk, J.E.

The Journal of biological chemistry, 1973-02, Vol.248 (4), p.1301-1306 [Periódico revisado por pares]

Elsevier Inc

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  • Título:
    Mapping of the Active Sites of Transglutaminases
  • Autor: Gross, Michael ; Folk, J.E.
  • É parte de: The Journal of biological chemistry, 1973-02, Vol.248 (4), p.1301-1306
  • Descrição: Calcium-activated guinea pig liver transglutaminase catalyzes the incorporation of amines at the carboxamide group of several aliphatic amides. Initial velocity findings with n-valeramide and methylamine as substrates are consistent with a modified double displacement mechanism for this reaction. This mechanism has already been demonstrated for amine incorporation at the γ-carboxamide group of peptide-bound glutamine (Folk, J. E. (1969) J. Biol. Chem. 244, 3707). Inhibition patterns for aliphatic amides suggest that binding of these compounds occurs at the site in the enzyme to which the carboxamide side chain of peptide-bound glutamine residues attaches. All of the straight-chain amides tested proved to be substrates with the exception of formamide. Branched-chain amides in which there is a methyl group in the α or β position of the methylene side chain are not substrates; those with methyl groups on the γ-carbon of the side chain are. These observations and their consideration lead to the suggestion that peptide-bound glutamine attaches to the enzyme with its β and γ methylene groups situated in a hydrophobic binding region and with its carboxamide group directed toward the active site —SH group of the enzyme. The dimensions of this site preclude the productive binding of peptide-bound asparagine. An active site pocket of fixed dimensions into which the carboxamide group and methylene side chain of substrate must be injected and from which product must be extruded is not consistent with the substrate specificity of the enzyme or with the ready dissociation of many products. This, taken together with present observations, favors an hypothesis of an essential substrate-induced conformational change in the active site of the enzyme that precedes or accompanies enzyme acylation.
  • Editor: Elsevier Inc
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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