PDBsum entry 1tdy

Hydrolase (o-glycosyl)

PDB id: 1tdy

Contents

Protein chain

130 a.a. *

Waters ×74

* Residue conservation analysis

PDB id:

1tdy

Name:

Hydrolase (o-glycosyl)

Title:

Dissection of the functional role of structural elements of tyrosine- 63 in the catalytic action of human lysozyme

Structure:

Human lysozyme. Chain: a. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606

Resolution:

1.70Å R-factor: 0.181

Authors:

K.Harata,M.Muraki,Y.Jigami

Key ref:

M.Muraki et al. (1992). Dissection of the functional role of structural elements of tyrosine-63 in the catalytic action of human lysozyme. Biochemistry, 31, 9212-9219. PubMed id: 1390708 DOI: 10.1021/bi00153a014

Date:

06-Aug-92 Release date: 15-Jan-93

Protein chain

P61626  (LYSC_HUMAN) -  Lysozyme C from Homo sapiens

Seq: 148 a.a.

Struc: 130 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.3.2.1.17 - lysozyme.
• Reaction: Hydrolysis of the 1,4-beta-linkages between N-acetyl-D-glucosamine and N-acetylmuramic acid in peptidoglycan heteropolymers of the prokaryotes cell walls.

DOI no: 10.1021/bi00153a014

Biochemistry 31:9212-9219 (1992)

PubMed id: 1390708

Dissection of the functional role of structural elements of tyrosine-63 in the catalytic action of human lysozyme.

M.Muraki, K.Harata, Y.Jigami.

ABSTRACT

The functional role of tyrosine-63 in the catalytic action of human lysozyme (EC 3.2.1.17) has been probed by site-directed mutagenesis. In order to identify the role of Tyr63 in the interaction with substrate, both the three-dimensional structures and the enzymatic functions of the mutants, in which Tyr63 was converted to phenylalanine, tryptophan, leucine, or alanine, have been characterized in comparison with those of the wild-type enzyme. X-ray crystallographical analysis of the mutant enzyme at not less than 1.77-A resolution indicated no remarkable change in tertiary structure except the side chain of 63rd residue. The conversion of Tyr63 to Phe or Trp did not change the enzymatic properties against the noncharged substrate (or substrate analogs) largely, while the conversion to Leu or Ala markedly reduced the catalytic activity to a few percent of wild-type enzyme. Kinetic analysis using p-nitrophenyl penta-N-acetyl-beta-(1----4)-chitopentaoside (PNP-(GlcNAc)5) as a substrate revealed that the reduction of activity should mainly be attributed to the reduction of affinity between enzyme and substrate. The apparent contribution of the phenolic hydroxyl group and the phenol group in the side chain of Tyr63 was estimated to 0.4 +/- 0.4 and 2.5 +/- 0.8 kcal mol-1, respectively. The result suggested that the direct contact between the planar side-chain group of Tyr63 and the sugar residue at subsite B is a major determinant of binding specificity toward a electrostatically neutral substrate in the catalytic action of human lysozyme.