TY - JOUR

T1 - Autoxidation and photooxidation of tetrahydrobiopterin: a theoretical study

AU - Buglak, Andrey A.

AU - Telegina, Taisiya A.

AU - Vechtomova, Yulia L.

AU - Kritsky, Mikhail S.

N1 - Publisher Copyright: © 2021 Informa UK Limited, trading as Taylor & Francis Group.

PY - 2021/5/4

Y1 - 2021/5/4

N2 - Pterins are naturally occurring pigments and enzyme cofactors widespread in living organisms. Tetrahydrobiopterin (H(4)Bip) is a coenzyme of aromatic amino acid hydroxylases, NO-synthases, and alkylglycerol monooxygenases. This coenzyme is prone to oxidation in the presence of molecular oxygen, a so-called autoxidation. The reactions participating in H(4)Bip autoxidation are well known. However, our study is an attempt to evaluate theoretically the feasibility of reactions participating in autoxidation. To do so, we have calculated the Gibbs free energy of elementary reactions between H(4)Bip, its derivatives, molecular oxygen, and reactive oxygen species (ROS). In the last few years, we have established the photosensitized oxidation of H(4)Bip experimentally. Thus, we have also evaluated the feasibility of H(4)Bip photooxidation reactions, which may occur according to both type-I and type-II photosensitized oxidation. We calculated Fukui indices for H(4)Bip and found particular atoms in the molecule that interact with nucleophiles (for example, singlet oxygen O-1(2)) and radicals (in particular, molecular oxygen O-3(2)). Therefore, we evaluated the probability of H(4)Bip autoxidation reactions, photooxidation reactions, and the reactivity of particular atoms in H(4)Bip molecule using the theoretical methods of quantum chemistry.

AB - Pterins are naturally occurring pigments and enzyme cofactors widespread in living organisms. Tetrahydrobiopterin (H(4)Bip) is a coenzyme of aromatic amino acid hydroxylases, NO-synthases, and alkylglycerol monooxygenases. This coenzyme is prone to oxidation in the presence of molecular oxygen, a so-called autoxidation. The reactions participating in H(4)Bip autoxidation are well known. However, our study is an attempt to evaluate theoretically the feasibility of reactions participating in autoxidation. To do so, we have calculated the Gibbs free energy of elementary reactions between H(4)Bip, its derivatives, molecular oxygen, and reactive oxygen species (ROS). In the last few years, we have established the photosensitized oxidation of H(4)Bip experimentally. Thus, we have also evaluated the feasibility of H(4)Bip photooxidation reactions, which may occur according to both type-I and type-II photosensitized oxidation. We calculated Fukui indices for H(4)Bip and found particular atoms in the molecule that interact with nucleophiles (for example, singlet oxygen O-1(2)) and radicals (in particular, molecular oxygen O-3(2)). Therefore, we evaluated the probability of H(4)Bip autoxidation reactions, photooxidation reactions, and the reactivity of particular atoms in H(4)Bip molecule using the theoretical methods of quantum chemistry.

KW - Gibbs free energy

KW - Tetrahydrobiopterin autoxidation

KW - density functional theory

KW - molecular oxygen

KW - photooxidation

KW - Gibbs free energy

KW - Tetrahydrobiopterin autoxidation

KW - density functional theory

KW - molecular oxygen

KW - photooxidation

KW - PTERINS

KW - ACID

KW - MECHANISM

KW - THERMOCHEMISTRY

KW - TYROSINASE

KW - TETRAHYDROPTERIDINES

KW - KINETICS

KW - GAS-PHASE

KW - NITRIC-OXIDE

KW - 6-TETRAHYDROBIOPTERIN

UR - http://www.scopus.com/inward/record.url?scp=85115157993&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/0fffdc8f-3902-30f8-a8d4-9f0aa9475096/

U2 - 10.1080/10715762.2020.1860213

DO - 10.1080/10715762.2020.1860213

M3 - Article

C2 - 33283562

VL - 55

SP - 499

EP - 509

JO - Free Radical Research

JF - Free Radical Research

SN - 1071-5762

IS - 5

ER -