Amino acids structural analogues

Non-competitive Infubitors Among Amino-acid Structural Analogues... 

The yellow analogues, the betaxanthins, are composed of betalamic acid with amino acids or amines, respectively, amounting to 26 structures known to occur naturally. " Structures unambiguously assigned by NMR spectroscopy usually carry trivial names derived from the plant material from which they have been first isolated. The substitution patterns of betalyanins and betaxanthins hitherto reported together with their particular plant sources are listed in Table 4.4.1 and 4.4.2, respectively. 

Hilvert s group used the same hapten [26] with a different spacer to generate an antibody catalyst which has very different thermodynamic parameters. It has a high entropy of activation but an enthalpy lower than that of the wild-type enzyme (Table 1, Antibody 1F7, Appendix entry 13.2a) (Hilvert et al., 1988 Hilvert and Nared, 1988). Wilson has determined an X-ray crystal structure for the Fab fragment of this antibody in a binary complex with its TSA (Haynes et al., 1994) which shows that amino acid residues in the active site of the antibody catalyst faithfully complement the components of the conformationally ordered transition state analogue (Fig. 11) while a trapped water molecule is probably responsible for the adverse entropy of activation. Thus it appears that antibodies have emulated enzymes in finding contrasting solutions to the same catalytic problem. 

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