PDBsum entry 2acu

Oxidoreductase

PDB id: 2acu

Contents

Protein chain

315 a.a. *

Ligands

NAP

CIT

Waters ×142

* Residue conservation analysis

PDB id:

2acu

Name:

Oxidoreductase

Title:

Tyrosine-48 is the proton donor and histidine-110 directs substrate stereochemical selectivity in the reduction reaction of human aldose reductase: enzyme kinetics and the crystal structure of the y48h mutant enzyme

Structure:

Aldose reductase. Chain: a. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

1.76Å R-factor: 0.187

Authors:

K.M.Bohren,C.E.Grimshaw,C.-J.Lai,K.H.Gabbay,G.A.Petsko,D.H.Harrison, D.Ringe

Key ref:

K.M.Bohren et al. (1994). Tyrosine-48 is the proton donor and histidine-110 directs substrate stereochemical selectivity in the reduction reaction of human aldose reductase: enzyme kinetics and crystal structure of the Y48H mutant enzyme. Biochemistry, 33, 2021-2032. PubMed id: 8117659 DOI: 10.1021/bi00174a007

Date:

15-Apr-94 Release date: 31-Jul-94

Protein chain

P15121  (ALDR_HUMAN) -  Aldo-keto reductase family 1 member B1 from Homo sapiens

Seq: 316 a.a.

Struc: 315 a.a.*

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

Enzyme reactions

• Enzyme class 1: E.C.1.1.1.21 - aldose reductase.
• Reaction:
  1. an alditol + NAD⁺ = an aldose + NADH + H⁺
  2. an alditol + NADP⁺ = an aldose + NADPH + H⁺

alditol + NAD(+) (Bound ligand (Het Group name = NAP) matches with 91.67% similarity) = aldose + NADH + H(+)

alditol + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = aldose + NADPH + H(+)

• Enzyme class 2: E.C.1.1.1.300 - NADP-retinol dehydrogenase.
• Reaction: all-trans-retinol + NADP⁺ = all-trans-retinal + NADPH + H⁺

all-trans-retinol + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = all-trans-retinal + NADPH + H(+)

• Enzyme class 3: E.C.1.1.1.372 - D/L-glyceraldehyde reductase.
• Reaction:
  1. glycerol + NADP⁺ = L-glyceraldehyde + NADPH + H⁺
  2. glycerol + NADP⁺ = D-glyceraldehyde + NADPH + H⁺

glycerol + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = L-glyceraldehyde + NADPH + H(+)

glycerol + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = D-glyceraldehyde + NADPH + H(+)

• Enzyme class 4: E.C.1.1.1.54 - allyl-alcohol dehydrogenase.
• Reaction: allyl alcohol + NADP⁺ = acrolein + NADPH + H⁺

allyl alcohol + NADP(+) (Bound ligand (Het Group name = NAP) corresponds exactly) = acrolein + NADPH + H(+)

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi00174a007

Biochemistry 33:2021-2032 (1994)

PubMed id: 8117659

Tyrosine-48 is the proton donor and histidine-110 directs substrate stereochemical selectivity in the reduction reaction of human aldose reductase: enzyme kinetics and crystal structure of the Y48H mutant enzyme.

K.M.Bohren, C.E.Grimshaw, C.J.Lai, D.H.Harrison, D.Ringe, G.A.Petsko, K.H.Gabbay.

ABSTRACT

The active site of human aldose reductase contains two residues, His110 and Tyr48, either of which could be the proton donor during catalysis. Tyr48 is a candidate since its hydroxyl group is in proximity to Lys77 and thus may have an abnormally low pKa value. To distinguish between these possibilities, we used site-directed mutagenesis to create the H110Q and H110A, the Y48F, Y48H, and Y48S, and the K77M mutant enzymes. The two His110 mutants resulted in a 1000-20,000-fold drop in kcat/Km, respectively, for the reduction of DL-glyceraldehyde at pH 7. The Y48F mutation caused total loss of activity, whereas the Y48H and Y48S mutants retained catalytic activity with kcat/Km reduced by 5 orders of magnitude. The K77M mutant is an inactive enzyme. Kinetic studies using xylose stereoisomers show that the wild-type enzyme distinguishes between D-xylose, L-xylose, and D-lyxose up to 150-fold better than the H110A or H110Q mutants. The His110 mutants do not effectively discriminate between these isomers (4-11-fold). The crystal structure of the Y48H mutant refined at 1.8-A resolution shows that the overall structure is not significantly different from the wild-type structure. Electron densities for the histidine side chain and a new water molecule fill the space occupied by Tyr48 in the wild-type enzyme. The water molecule is in hydrogen-bonding distance to the N zeta group of Lys77 and to the N epsilon of His48 and fills the space occupied by the hydroxyl group of tyrosine in the wild-type structure. These findings suggest that proton transfer is mediated in the Y48H mutant enzyme by the water molecule. The Y48H mutant shows large and equal primary deuterium isotope effects on kcat and kcat/Km (1.81 +/- 0.03), providing direct evidence for hydride transfer as the rate-determining step in this mutant. Deuterium solvent isotope effects indicate that the relative contribution of proton transfer to this step of the catalytic cascade is much less important for the Y48H mutant than for the wild-type enzyme [D2O(kcat/Km) = 1.06 +/- 0.02 and 4.73 +/- 0.23, respectively]. The kinetic and mutagenesis data, together with structural data, indicate that His 110 plays an important role in the orientation of substrates in the active site pocket, while Tyr48 is the proton donor during aldehyde reduction by aldose reductase.