Studies on 3‐Deoxy‐d‐arabinoheptulosonate‐7‐phosphate Synthetase(phe) from Escherichia coli K12

Publisher Website
Google Scholar
Abstract
Investigations with structural analogs of phenylalanine indicated an absolute requirement for the aromatic ring, the .alpha.-carboxyl and .alpha.-amino groups of phenylalanine for inhibition of 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase(phe) [EC 4.1.2.15] activity. Replacement of the .alpha.-H atom with a methyl group does not decrease the inhibition greatly. Varying degrees of inhibition were observed with o, m and p mono-substituted fluoro, chloro and hydroxy phenylalanines. D-Phenylalanine and several metabolites of the aromatic biosynthetic pathways do not inhibit enzymic activity. Circular dichroism studies indicated that the native enzyme possesses .apprx. 26% .alpha.-helix. Circular dichroic and UV difference spectra indicated that the addition of phenylalanine to the synthetase induces a conformational change involving a small alteration of the secondary structure and large alterations in the interactions of some of the aromatic residues of the enzyme. In particular, a tryptophan residue moves from an extremely hydrophobic environment to one less hydrophobic. Kd for the binding of phenylalanine to the enzyme was determined spectrophotometrically to be 75 .mu.M. Chemical modification studies suggested that a sulfhydryl group and possibly a lysine residue may be implicated in the catalytic activity of the enzyme.

This publication has 16 references indexed in Scilit: