Stereoselective Bimolecular Phenoxy Radical Coupling by an Auxiliary (Dirigent) Protein Without an Active Center

The discovery of dirigent proteins (DPs) and their functions in plant phenol biochemistry was made over two decades ago with Forsythia × intermedia. Stereo-selective, DP-guided, monolignol-derived radical coupling in vitro...

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Unexpected polymerization mechanism of dilignol in the lignin growing

Royal Society Open Science ◽

10.1098/rsos.190445 ◽

2019 ◽

Vol 6 (7) ◽

pp. 190445 ◽

Cited By ~ 2

Author(s):

Yasuyuki Matsushita ◽

Yuto Oyabu ◽

Dan Aoki ◽

Kazuhiko Fukushima

Keyword(s):

Reaction Mechanism ◽

Higher Plants ◽

Phenoxy Radical ◽

Covalent Linkage ◽

Polymerization Mechanism ◽

Essential Component ◽

Radical Coupling ◽

Unexpected Reaction ◽

Lignin Polymerization ◽

Dehydrogenative Polymerization

Lignin is an essential component of higher plants, which is built by the enzymatic dehydrogenative polymerization of monolignols. First, monolignol is enzymatically oxidized to produce the phenoxy radical, which can form resonance hybrids. Two radical resonant hybrids are coupled with each other to yield dilignol with various linkage types, of which the main structures are β- O -4′ ( I ), β-5′ ( II ) and β-β′ ( III ). However, the reaction mechanism behind the addition lignol radicals to dilignol is not yet fully understood. Here, we show an unexpected reaction with structure II during enzymatic dehydrogenative polymerization, which involves cleavage of a covalent linkage and creation of a new radical coupling site. This implied that the β-5 dilignol diversifies the growing pattern of lignin. This discovery elucidates a novel mechanism in lignin polymerization.

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Kinetic Study of the Effect of Heparin on the Amidase Activity of Trypsin, Plasmin and Urokinase

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657362 ◽

1983 ◽

Vol 49 (03) ◽

pp. 199-203 ◽

Cited By ~ 10

Author(s):

V M Yomtova ◽

N A Stambolieva ◽

B M Blagoev

Keyword(s):

Kinetic Study ◽

Active Center ◽

Simultaneous Presence ◽

Amidase Activity ◽

Competitive Inhibitors ◽

Uncompetitive Inhibitor

SummaryIt was found that the effect of heparin on the amidase activity of urokinase (E C 3.4.21.31), plasmin (E C 3.4.21.7) and trypsin (E C 3.4.21.4) depended on the substrate used. No effect of heparin on the amidase activity of urokinase and trypsin was observed when Pyro Glu-Gly-Arg-p-nitroanilide (S-2444) and α-N-acetyl-L-lysine-p-nitroanilide (ALNA) were used as substrates. Heparin acted as a uncompetitive inhibitor of trypsin (Ki = 1.2×10-6 M), plasmin (Ki = 4.9×10-6 M) and urokinase (Ki = l.0×10-7 M) when Bz-Phe-Val-Arg-p-nitroanilide (S-2160), H-D-Val-Leu-Lys-p-nitroanilide (S-2251) and plasminogen, respectively, were used as substrates. These results, as well as the data obtained by studying the effect of the simultaneous presence of heparin and competitive inhibitors suggest that although heparin is not bound at the active center of these enzymes, it may influence the effectivity of catalysis.

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Matrix metalloproteinases: structure, functions and genetic polymorphism

Nauchno-prakticheskii zhurnal «Patogenez» ◽

10.25557/gm.2017.2.7297 ◽

2017 ◽

pp. 14-23

Author(s):

А.С. Шадрина ◽

И.В. Терешкина ◽

Я.З. Плиева ◽

Д.Н. Кушлинский ◽

Д.О. Уткин ◽

...

Keyword(s):

Genetic Polymorphism ◽

Matrix Metalloproteinases ◽

Active Center ◽

Human Body ◽

Enzymatic Catalysis ◽

Structure Functions ◽

Zinc Ion ◽

Etiological Factors ◽

Mmp Genes

Матриксные металлопротеиназы (ММП) - ферменты класса гидролаз, осуществляющие ферментативный катализ с помощью связанного в активном центре иона цинка. Функции ММП разнообразны, и нарушение баланса их активности может быть одним из этиологических факторов различных заболеваний. В данном обзоре рассмотрена классификация ММП человека, особенности их структуры и регуляции, а также роль в физиологических и патологических процессах в организме человека. Приведен перечень наиболее изученных на настоящий момент полиморфных вариантов генов MMП, описаны их функциональные эффекты и представлены результаты ассоциативных исследований. Matrix metalloproteinases (MMPs) are enzymes of the hydrolase class that carry out enzymatic catalysis with the help of a zinc ion bound in the active center. MMP functions are diverse, and a disturbance in the balance of their activity may be one of the etiological factors of various diseases. In this review, the classification of human MMP, the features of their structure and regulation, as well as the role in physiological and pathological processes in the human body are considered. A list of the most studied polymorphic versions of MMP genes has been given, their functional effects have been described, and the results of associative studies have been presented.

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Quantum Mechanical Calculations Suggest That Lignin Polymerization Is Kinetically Controlled

10.26434/chemrxiv.7334564.v2 ◽

2019 ◽

Author(s):

Terry Gani ◽

Michael Orella ◽

Eric Anderson ◽

Michael Stone ◽

Fikile Brushett ◽

...

Keyword(s):

Plant Cell ◽

First Principles ◽

Plant Cell Wall ◽

Biological Processes ◽

Plant Cell Walls ◽

Biomass Valorization ◽

Effective Strategies ◽

Radical Coupling ◽

Kinetically Controlled ◽

Atomistic Models

Lignin is an abundant biopolymer important for plant function while holding promise as a renewable source of valuable chemicals. Although the lignification process in plant cell walls has been long-studied, a comprehensive, mechanistic understanding on the molecular scale remains elusive. A better understanding of lignification will lead to improved atomistic models of the plant cell wall that could, in turn, inform effective strategies for biomass valorization. Here, using first-principles quantum chemical calculations, we show that a simple model of kinetically-controlled radical coupling broadly rationalizes qualitative experimental observations of lignin structure across a wide variety of biomass types, thus paving the way for predictive, first-principles models of lignification while highlighting the ability of computational chemistry to help illuminate complex biological processes.

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