Summary
The mechanism of activation of PLP-Lys aldimines of Aspartate aminotransferase (AspAT), aromatic amino acid aminotransferase (ArAT), and aromatic L-amino acid decarboxylase (AADC) to the ketoenamine form was studied. In AspAT and ArAT the aldimines exist as the nonprotonated form. Upon binding of substrate amino acids, the pK a of these aldimines are increased and the aldimines become the protonated, ketoenamine form, which is considered to be favorable for transaldimination. The increase in pK a by binding of amino acids was proved by mutagenesis studies to be mediated mainly by interaction of α-carboxylate group of the substrate and Arg386 of the enzymes. In AADC, the aldimine is protonated, but it exists as the enolimine tautomer and is not favorable for transaldimination. In the presence of a substrate amino acid, it undergoes tautomerization to the ketoenamine form. Pyridoxal enzymes show a variety of spectra, and PLP-Lys aldimines exist as several protonated/deprotonated forms. However, it is proposed that all these forms are converted to the protonated, ketoenamine form upon binding of substrate amino acids, either by altering the pK a values of the PLP-Lys aldimines or by changing the polarity of the microenvironment around the aldimines.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Goldberg, J.M., Swanson, R.V., Goodman, H.S. and Kirsch, J.F. (1991) Structure of the complex between pyridoxal 5’-phosphate and the tyrosine 225 to phenylalanine mutant of Escherichia coli aspartate aminotransferase determined by isotope-edited classical Raman difference spectroscopy. Biochemistry 30: 305–312.
Hayashi, H., Mizuguchi, H. and Kagamiyama, H. (1993a) Rat liver aromatic L-amino acid decarboxylase: Spectroscopic and kinetic analysis of the coenzyme and reaction intermediates. Biochemistry 32: 812–818.
Hayashi, H., Inoue, K., Nagata, T., Kuramitsu, S. and Kagamiyama, H. (1993b) Escherichia coli aromatic amino acid aminotransferase: Characterization and comparison with aspartate aminotransferase. Biochemistry 32: 12229–12239.
Iwasaki, M., Hayashi, H. and Kagamiyama, H. (1994) Protonation state of the active-site Schiff base of aromatic amino acid aminotransferase: Modulation by binding of ligands and implications for its role in catalysis. J. Biochem. 115: 156–161.
Kallen, R.G., Korpela, T., Martell, A.E., Matsushima, Y., Metzler, C.M., Metzler, D.E., Morozov, Yu.V., Ralston, I.M., Savin, F.A., Torchinsky, Yu.M. and Ueno, H. (1985) Chemical and spectroscopic properties of pyridoxal and pyridoxamine phosphates. in Transaminases ( Christen, P., & Metzler, D.E., Eds.) pp 37–108, John Wiley & Sons, New York.
Kamitori, S., Hirotsu, K., Higuchi, T., Kondo, K., Inoue, K., Kuramitsu, S., Kagamiyama, H., Higuchi, Y., Yasuoka, N., Kusunoki, M., H. and Matsuura, Y. (1987) Overproduction and preliminary X-ray characterization of aspartate aminotransferase from Escherichia coli. J. Biochem. 101: 813–816.
Kamitori, S., Okamoto, A., Hirotsu, K., Higuchi, T., Kuramitsu, S., Kagamiyama, H., Matsuura, Y. and Katsube, Y. (1990) Three-dimensional structure of aspartate aminotransferase from Escherichia coli and its mutant enzyme at 2.5 A resolution. J. Biochem. 108: 175–184.
Kirsch, J.F., Eichele, G., Ford, G.C., Vincent, M.G., Jansonius, J.N., Gehring, H. and Christen, P. (1984) Mechanism of action of aspartate aminotransferase proposed on the basis off its spatial structure. J. Mol. Biol. 174: 497–525.
Martin, R.G. (1970) Imidazolylacetolphosphate: L-glutamate aminotransferase—Mechanism of Action. Arch. Biochem. Biophys. 138: 239–244.
Metzler, D.E. (1977) Biochemistry, pp. 444–461, Academic Press, New York.
Metzler, C. M., Viswanath, R. and Metzler, D. E. (1991). Equilibria and absorption spectra of tryptophanase. J. Biol. Chem. 266: 9374–9381.
O’Leary, M.H. (1971) A proposed structure for the 330-nm chromophore of glutamate decarboxylase and other pyridoxal 5’-phosphate dependent enzymes. Biochim. Biophys. Acta 242: 484–492
Snell, E.E. (1985) Pyridoxal phosphate in nonenzymic and enzymic reactions. in Transaminases ( Christen, P., & Metzler, D.E., Eds.) pp 19–35, John Wiley & Sons, New York.
Voltattorni, C.B., Minelli, A., Vecchini, P., Fiori, A. and Turano, C. (1979) Purification and characterization of 3,4-dihydroxyphenylalanine decarboxylase from pig kidney. Eur. J. Biochem. 93: 181–188.
Yano, T., Kuramitsu, S., Tanase, S., Morino, Y. and Kagamiyama, H. (1992) Role of Asp222 in the catalytic mechanism of Escherichia coli aspartate aminotransferase: The amino acid residue which enhances the function of the enzyme-bound coenzyme pyridoxal 5’-phosphate. Biochemistry 31: 5878–5887.
Yano, T., Mizuno, T. and Kagamiyama, H. (1993) A hydrogen-bonding network modulating enzyme function: asparagine-194 and tyrosine-225 of Escherichia coli aspartate aminotransferase. Biochemistry 32: 1810–1815.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1994 Birkhäuser Verlag Basel/Switzerland
About this paper
Cite this paper
Kagamiyama, H., Hayashi, H., Yano, T., Mizuguchi, H., Ishii, S. (1994). Enzyme-substrate interactions modulating protonation and tautomerization states of the aldimines of pyridoxal enzymes. In: Marino, G., Sannia, G., Bossa, F. (eds) Biochemistry of Vitamin B6 and PQQ. Advances in Life Sciences. Birkhäuser Basel. https://doi.org/10.1007/978-3-0348-7393-2_7
Download citation
DOI: https://doi.org/10.1007/978-3-0348-7393-2_7
Publisher Name: Birkhäuser Basel
Print ISBN: 978-3-0348-7395-6
Online ISBN: 978-3-0348-7393-2
eBook Packages: Springer Book Archive