Original scientific paper

The (- + -) Charge Distribution: A Common Pattern in the Transition State of Some Enzymes

Gabor Naray-Szabo ; Department of Theoretical Chemistry, Eotvos Lortind University Budapest, H-l117 Budapest, Pazmany Peter st. 2, Hungary
Timea Gerczei ; Department of Theoretical Chemistry, Eotvos Lortind University Budapest, H-l117 Budapest, Pazmany Peter st. 2, Hungary

Abstract

X-ray diffraction and molecular modelling studies in the la st two
decades have drawn attention to the (- + -) charge distribution
that plays an important role in some enzymatic processes. In most
cases two of the charged moieties are amino-acid side chains of the
enzyme, where the positive and negative charges are provided by
a protonated His and by the deprotonated carboxylic group of an
Asp or Glu side chain, respectively. The third group is the substrate
itself, getting negatively charged during the catalytic process.
Several enzymes (e.g. serine proteases, acetylcholinesterase
and lipases) make use of the Ser-His-Asp(Glu) triad as a central
machinery in the catalysis offering the serine oxygen, which attacks
the substrate to yield the tetrahedral intermediate, as the negative charge in the above pattern. In the ring opening step of xylose isomerase catalysis, this serine oxygen is replaced by the 01
oxygen atom of the glucopyranose substrate. In the case of
lysozyme, an Asp and a Glu side chain encounter the positively
charged sugar ring of the substrate, thus providing the (- + -) distribution. In the present paper, we discuss the role of the surrounding protein core in the electrostatic stabilization of the above pattern. We call attention to the possibility of convergent evolution
which provides not only the conserved charge distribution but also
a template by the protein environment stabilizing it electrostatically,
i.e. through interactions between atomic net charges, hydrogen
bonds and u-helix dipole effects.

Keywords

Hrčak ID:

177124

URI

https://hrcak.srce.hr/177124

Publication date:

1.11.1996.

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