3ypi
From Proteopedia
(New page: 200px<br /><applet load="3ypi" size="450" color="white" frame="true" align="right" spinBox="true" caption="3ypi, resolution 2.8Å" /> '''ELECTROPHILIC CATALYS...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:3ypi.jpg|left|200px]]<br /><applet load="3ypi" size=" | + | [[Image:3ypi.jpg|left|200px]]<br /><applet load="3ypi" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="3ypi, resolution 2.8Å" /> | caption="3ypi, resolution 2.8Å" /> | ||
'''ELECTROPHILIC CATALYSIS IN TRIOSEPHOSPHASE ISOMERASE: THE ROLE OF HISTIDINE-95'''<br /> | '''ELECTROPHILIC CATALYSIS IN TRIOSEPHOSPHASE ISOMERASE: THE ROLE OF HISTIDINE-95'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Electrophilic catalysis by histidine-95 in triosephosphate isomerase has | + | Electrophilic catalysis by histidine-95 in triosephosphate isomerase has been probed by using Fourier transform infrared spectroscopy and X-ray crystallography. The carbonyl stretching frequency of dihydroxyacetone phosphate bound to the wild-type enzyme is known to be 19 cm-1 lower (at 1713 cm-1) than that of dihydroxyacetone phosphate free in solution (at 1732 cm-1), and this decrease in stretching frequency has been ascribed to an enzymic electrophile that polarizes the substrate carbonyl group toward the transition state for the enolization. Infrared spectra of substrate bound to two site-directed mutants of yeast triosephosphate isomerase in which histidine-95 has been changed to glutamine or to asparagine show unperturbed carbonyl stretching frequencies between 1732 and 1742 cm-1. The lack of carbonyl polarization when histidine-95 is removed suggests that histidine-95 is indeed the catalytic electrophile, at least for dihydroxyacetone phosphate. Kinetic studies of the glutamine mutant (H95Q) have shown that the enzyme follows a subtly different mechanism of proton transfers involving only a single acid-base catalytic group. These findings suggest an additional role for histidine-95 as a general acid-base catalyst in the wild-type enzyme. The X-ray crystal structure of the H95Q mutant with an intermediate analogue, phosphoglycolohydroxamate, bound at the active site has been solved to 2.8-A resolution, and this structure clearly implicates glutamate-165, the catalytic base in the wild-type isomerase, as the sole acid-base catalyst for the mutant enzyme.(ABSTRACT TRUNCATED AT 250 WORDS) |
==About this Structure== | ==About this Structure== | ||
| - | 3YPI is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae] with PGH as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Triose-phosphate_isomerase Triose-phosphate isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.1 5.3.1.1] Full crystallographic information is available from [http:// | + | 3YPI is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Saccharomyces_cerevisiae Saccharomyces cerevisiae] with <scene name='pdbligand=PGH:'>PGH</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Triose-phosphate_isomerase Triose-phosphate isomerase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.3.1.1 5.3.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3YPI OCA]. |
==Reference== | ==Reference== | ||
| Line 15: | Line 15: | ||
[[Category: Triose-phosphate isomerase]] | [[Category: Triose-phosphate isomerase]] | ||
[[Category: Lolis, E.]] | [[Category: Lolis, E.]] | ||
| - | [[Category: Petsko, G | + | [[Category: Petsko, G A.]] |
[[Category: PGH]] | [[Category: PGH]] | ||
[[Category: isomerase(intramolecular oxidoreductse)]] | [[Category: isomerase(intramolecular oxidoreductse)]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 19:11:50 2008'' |
Revision as of 17:11, 21 February 2008
|
ELECTROPHILIC CATALYSIS IN TRIOSEPHOSPHASE ISOMERASE: THE ROLE OF HISTIDINE-95
Overview
Electrophilic catalysis by histidine-95 in triosephosphate isomerase has been probed by using Fourier transform infrared spectroscopy and X-ray crystallography. The carbonyl stretching frequency of dihydroxyacetone phosphate bound to the wild-type enzyme is known to be 19 cm-1 lower (at 1713 cm-1) than that of dihydroxyacetone phosphate free in solution (at 1732 cm-1), and this decrease in stretching frequency has been ascribed to an enzymic electrophile that polarizes the substrate carbonyl group toward the transition state for the enolization. Infrared spectra of substrate bound to two site-directed mutants of yeast triosephosphate isomerase in which histidine-95 has been changed to glutamine or to asparagine show unperturbed carbonyl stretching frequencies between 1732 and 1742 cm-1. The lack of carbonyl polarization when histidine-95 is removed suggests that histidine-95 is indeed the catalytic electrophile, at least for dihydroxyacetone phosphate. Kinetic studies of the glutamine mutant (H95Q) have shown that the enzyme follows a subtly different mechanism of proton transfers involving only a single acid-base catalytic group. These findings suggest an additional role for histidine-95 as a general acid-base catalyst in the wild-type enzyme. The X-ray crystal structure of the H95Q mutant with an intermediate analogue, phosphoglycolohydroxamate, bound at the active site has been solved to 2.8-A resolution, and this structure clearly implicates glutamate-165, the catalytic base in the wild-type isomerase, as the sole acid-base catalyst for the mutant enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
About this Structure
3YPI is a Single protein structure of sequence from Saccharomyces cerevisiae with as ligand. Active as Triose-phosphate isomerase, with EC number 5.3.1.1 Full crystallographic information is available from OCA.
Reference
Electrophilic catalysis in triosephosphate isomerase: the role of histidine-95., Komives EA, Chang LC, Lolis E, Tilton RF, Petsko GA, Knowles JR, Biochemistry. 1991 Mar 26;30(12):3011-9. PMID:2007138
Page seeded by OCA on Thu Feb 21 19:11:50 2008
