scholarly journals Using Unnatural Amino Acids to Probe the Energetics of Oxyanion Hole Hydrogen Bonds in the Ketosteroid Isomerase Active Site

2014 ◽  
Vol 136 (21) ◽  
pp. 7643-7654 ◽  
Author(s):  
Aditya Natarajan ◽  
Jason P. Schwans ◽  
Daniel Herschlag
Keyword(s):  
Amino Acids ◽  
Hydrogen Bonds ◽  
Active Site ◽  
Unnatural Amino Acids ◽  
Ketosteroid Isomerase ◽  
Oxyanion Hole

scholarly journals Proton Affinity of the Oxyanion Hole in the Active Site of Ketosteroid Isomerase

Biochemistry ◽  
2010 ◽  
Vol 49 (12) ◽  
pp. 2725-2731 ◽  
Author(s):  
William Childs ◽  
Steven G. Boxer
Keyword(s):  
Proton Affinity ◽  
Active Site ◽  
Ketosteroid Isomerase ◽  
Oxyanion Hole

Improving Nature's Enzyme Active Site with Genetically Encoded Unnatural Amino Acids

2006 ◽  
Vol 128 (34) ◽  
pp. 11124-11127 ◽  
Author(s):  
Jennifer C. Jackson ◽  
Sean P. Duffy ◽  
Kenneth R. Hess ◽  
Ryan A. Mehl
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
Unnatural Amino Acids ◽  
Enzyme Active Site

scholarly journals Testing Geometrical Discrimination within an Enzyme Active Site: Constrained Hydrogen Bonding in the Ketosteroid Isomerase Oxyanion Hole

2008 ◽  
Vol 130 (41) ◽  
pp. 13696-13708 ◽  
Author(s):  
Paul A. Sigala ◽  
Daniel A. Kraut ◽  
Jose M. M. Caaveiro ◽  
Brandon Pybus ◽  
Eliza A. Ruben ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Active Site ◽  
Ketosteroid Isomerase ◽  
Oxyanion Hole ◽  
Enzyme Active Site

scholarly journals Active-Site Engineering of ω-Transaminase for Production of Unnatural Amino Acids Carrying a Side Chain Bulkier than an Ethyl Substituent

2015 ◽  
Vol 81 (20) ◽  
pp. 6994-7002 ◽  
Author(s):  
Sang-Woo Han ◽  
Eul-Soo Park ◽  
Joo-Young Dong ◽  
Jong-Shik Shin
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
Unnatural Amino Acids ◽  
Kinetic Resolution ◽  
Enantiomeric Excess ◽  
Active Site Residues ◽  
Alanine Scanning Mutagenesis ◽  
Content Type ◽  
Keto Acids ◽  
Steric Constraint

ABSTRACTω-Transaminase (ω-TA) is a promising enzyme for use in the production of unnatural amino acids from keto acids using cheap amino donors such as isopropylamine. The small substrate-binding pocket of most ω-TAs permits entry of substituents no larger than an ethyl group, which presents a significant challenge to the preparation of structurally diverse unnatural amino acids. Here we report on the engineering of an (S)-selective ω-TA fromOchrobactrum anthropi(OATA) to reduce the steric constraint and thereby allow the small pocket to readily accept bulky substituents. On the basis of a docking model in whichl-alanine was used as a ligand, nine active-site residues were selected for alanine scanning mutagenesis. Among the resulting variants, an L57A variant showed dramatic activity improvements in activity for α-keto acids and α-amino acids carrying substituents whose bulk is up to that of ann-butyl substituent (e.g., 48- and 56-fold increases in activity for 2-oxopentanoic acid andl-norvaline, respectively). An L57G mutation also relieved the steric constraint but did so much less than the L57A mutation did. In contrast, an L57V substitution failed to induce the improvements in activity for bulky substrates. Molecular modeling suggested that the alanine substitution of L57, located in a large pocket, induces an altered binding orientation of an α-carboxyl group and thereby provides more room to the small pocket. The synthetic utility of the L57A variant was demonstrated by carrying out the production of optically purel- andd-norvaline (i.e., enantiomeric excess [ee] > 99%) by asymmetric amination of 2-oxopantanoic acid and kinetic resolution of racemic norvaline, respectively.

scholarly journals Application of the quantum theory of atoms in molecules (QTAIM) to the study of the enzymatic kinetic resolution of propranolol, an amino alcohol with pharmaceutical applications

2020 ◽  
Author(s):  
D.A. Rincón ◽  
M.C. Daza ◽  
M. Doerr
Keyword(s):  
Quantum Theory ◽  
Hydrogen Bonds ◽  
Active Site ◽  
Kinetic Resolution ◽  
Catalytic Triad ◽  
Enantiomeric Purity ◽  
Atoms In Molecules ◽  
Racemic Mixture ◽  
Oxyanion Hole ◽  
Adrenergic Antagonist

Propranolol, ((R,S)-1-iso-propylamino-3-(1-naphthoxy)-2-propanol), is a β-adrenergic antagonist and is commercially available as a racemic mixture. Only the S-enantiomer has the desired therapeutic effect. Therefore, many researchers have been working on strategies to obtain S-propranolol with high enantiomeric purity. One approach to carry out the acetylation of (R,S)-Propranolol using Candida antarctica lipase B, CalB. This reaction leads to an enantiomeric purity of 96% at a relatively low conversion rate of 30 %. In our research group, we have been studying this reaction. The CalB active site is composed by the triad catalytic (ASP 187, HIS 224 and SER 105) and oxyanion hole (GLN 106 and THR 40). In a previous work, a QM/MM (Quantum Mechanics / Molecular Mechanics) study was carried out, using a QM region consisting only of the catalytic triad of CalB and (R,S)-propranolol [1]. In the present study, we investigate the effect of expanding the quantum region to include the oxyanion hole and to comprehend the effect of intermolecular hydrogen bonds present between the (R,S)-propranolol and the CalB active site. The electronic structure was analyzed using the Quantum Theory of Atoms In Molecules, QTAIM. Our results show that: 1. the studied reactions are more exothermic with the inclusion of the oxyanion hole than with only the catalytic triad. 2. the intermolecular interactions between (R,S)-propranolol and the CalB active site are dominated by hydrogen bonds (HB). Among those HBs, only one between propranolol and HIS 224, and another one between THR 40 and the carbonyl oxygen of acetylated SER 105 play an important role.

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