Unveiling the kinetic versatility of aryl-alcohol oxidases with different electron acceptors.

Aryl-alcohol oxidase (AAO) shows a pronounced duality as oxidase and dehydrogenase similar to that described for other glucose-methanol-choline (GMC) oxidase/dehydrogenase superfamily proteins involved in lignocellulose decomposition. In this work, we detail the overall mechanism of AAOs from and for catalyzing the oxidation of natural aryl-alcohol substrates using either oxygen or quinones as electron acceptors and describe the crystallographic structure of AAO from in complex with a product analogue. Kinetic studies with 4-methoxybenzyl and 3-chloro-4- methoxybenzyl alcohols, including both transient-state and steady-state analyses, along with interaction studies, provide insight into the oxidase and dehydrogenase mechanisms of these enzymes.

Expanding the Physiological Role of Aryl-Alcohol Flavooxidases as Quinone Reductases.

Aryl-alcohol oxidases (AAOs) are members of the glucose-methanol-choline oxidase/dehydrogenase (GMC) superfamily. These extracellular flavoproteins have been described as auxiliary enzymes in the degradation of lignin by several white-rot basidiomycetes. In this context, they oxidize fungal secondary metabolites and lignin-derived compounds using O as an electron acceptor, and supply HO to ligninolytic peroxidases.

A global phylogenomic analysis of the shiitake genus .

is a broadly distributed group of fungi that contains the cultivated shiitake mushroom, . We sequenced 24 genomes representing eight described species and several unnamed lineages of from 15 countries on four continents. comprises four major clades that arose in the Oligocene, three in the Americas and one in Asia-Australasia.

Engineering Peroxygenase for Epoxides Production from Vegetable Oil.

Vegetable oils are valuable renewable resources for the production of bio-based chemicals and intermediates, including reactive epoxides of industrial interest. Enzymes are an environmentally friendly alternative to chemical catalysis in oxygenation reactions, epoxidation included, with the added advantage of their potential selectivity. The unspecific peroxygenase of Collariella virescens is only available as a recombinant enzyme (rCviUPO), which is produced in Escherichia coli for protein engineering and analytical-scale optimization of plant lipid oxygenation.

Structural Characterization of Two Short Unspecific Peroxygenases: Two Different Dimeric Arrangements.

Unspecific peroxygenases (UPOs) are extracellular fungal enzymes of biotechnological interest as self-sufficient (and more stable) counterparts of cytochrome P450 monooxygenases, the latter being present in most living cells. Expression hosts and structural information are crucial for exploiting UPO diversity (over eight thousand UPO-type genes were identified in sequenced genomes) in target reactions of industrial interest. However, while many thousands of entries in the Protein Data Bank include molecular coordinates of P450 enzymes, only 19 entries correspond to UPO enzymes, and UPO structures from only two species ( and sp.

Regioselective and Stereoselective Epoxidation of n-3 and n-6 Fatty Acids by Fungal Peroxygenases.

Epoxide metabolites from n-3 and n-6 polyunsaturated fatty acids arouse interest thanks to their physiological and pharmacological activities. Their chemical synthesis has significant drawbacks, and enzymes emerge as an alternative with potentially higher selectivity and greener nature. Conversion of eleven eicosanoid, docosanoid, and other n-3/n-6 fatty acids into mono-epoxides by fungal unspecific peroxygenases (UPOs) is investigated, with emphasis on the (UPO) and (rUPO) enzymes.

Advances in enzymatic oxyfunctionalization of aliphatic compounds.

Selective oxyfunctionalizations of aliphatic compounds are difficult chemical reactions, where enzymes can play an important role due to their stereo- and regio-selectivity and operation under mild reaction conditions. P450 monooxygenases are well-known biocatalysts that mediate oxyfunctionalization reactions in different living organisms (from bacteria to humans). Unspecific peroxygenases (UPOs), discovered in fungi, have arisen as "dream biocatalysts" of great biotechnological interest because they catalyze the oxyfunctionalization of aliphatic and aromatic compounds, avoiding the necessity of expensive cofactors and regeneration systems, and only depending on HO for their catalysis.

Reaction mechanisms and applications of aryl-alcohol oxidase.

Aryl-alcohol oxidases (AAO) constitute a family of FAD-containing enzymes, included in the glucose-methanol-choline oxidase/dehydrogenase superfamily of proteins. They are commonly found in fungi, where their eco-physiological role is to produce hydrogen peroxide that activates ligninolytic peroxidases in white-rot (lignin-degrading) basidiomycetes or to trigger the Fenton reactions in brown-rot (carbohydrate-degrading) basidiomycetes. These enzymes catalyze the oxidation of a plethora of aromatic, and some aliphatic, polyunsaturated alcohols bearing conjugated primary hydroxyl group.

Changes in the Rhythm of Speech Difference between People with Nondegenerative Mild Cognitive Impairment and with Preclinical Dementia.

This study explores several speech parameters related to mild cognitive impairment, as well as those that might be flagging the presence of an underlying neurodegenerative process. Speech is an excellent biomarker because it is not invasive and, what is more, its analysis is rapid and economical. Our aim has been to ascertain whether the typical speech patterns of people with Alzheimer's disease are also present during the disorder's preclinical stages.

Two New Unspecific Peroxygenases from Heterologous Expression of Fungal Genes in Escherichia coli.

Unspecific peroxygenases (UPOs) constitute a new family of fungal heme-thiolate enzymes in which there is high biotechnological interest. Although several thousand genes encoding hypothetical UPO-type proteins have been identified in sequenced fungal genomes and other databases, only a few UPO enzymes have been experimentally characterized to date. Therefore, gene screening and heterologous expression from genetic databases are a priority in the search for UPOs for oxyfunctionalization reactions of interest.

Complete oxidation of hydroxymethylfurfural to furandicarboxylic acid by aryl-alcohol oxidase.

Background: 5-Hydroxymethylfurfural (HMF) is a highly valuable platform chemical that can be obtained from plant biomass carbohydrates. HMF can be oxidized to 2,5-furandicarboxylic acid (FDCA), which is used as a renewable substitute for the petroleum-based terephthalic acid in polymer production.

Results: Aryl-alcohol oxidase (AAO) from the white-rot fungus is able to oxidize HMF and its derivative 2,5-diformylfuran (DFF) producing formylfurancarboxylic acid (FFCA) thanks to its activity on benzylic alcohols and hydrated aldehydes.

Reversible Functional Changes Evoked by Anodal Epidural Direct Current Electrical Stimulation of the Rat Auditory Cortex.

Rat auditory cortex was subjected to 0.1 mA anodal direct current in seven 10-min sessions on alternate days. Based on the well-known auditory cortex control of olivocochlear regulation through corticofugal projections, auditory brainstem responses (ABRs) were recorded as an indirect test of the effectiveness and reversibility of the multisession protocol of epidural stimulation.

A Prototype for the Voice Analysis Diagnosis of Alzheimer's Disease.

Background: Speech variations enable us to map the performance of cognitive processes of syntactic, semantic, phonological, and articulatory planning and execution. Speaking is one of the first functions to be affected by neurodegenerative complaints such as Alzheimer's disease (AD), which makes the speech a highly promising biomarker for detecting the illness before the first preclinical symptoms appear.

Objective: This paper has sought to develop and validate a technological prototype that adopts an automated approach to speech analysis among older people.

Multiple implications of an active site phenylalanine in the catalysis of aryl-alcohol oxidase.

Aryl-alcohol oxidase (AAO) has demonstrated to be an enzyme with a bright future ahead due to its biotechnological potential in deracemisation of chiral compounds, production of bioplastic precursors and other reactions of interest. Expanding our understanding on the AAO reaction mechanisms, through the investigation of its structure-function relationships, is crucial for its exploitation as an industrial biocatalyst. In this regard, previous computational studies suggested an active role for AAO Phe397 at the active-site entrance.

Self-sustained enzymatic cascade for the production of 2,5-furandicarboxylic acid from 5-methoxymethylfurfural.

Background: 2,5-Furandicarboxylic acid is a renewable building block for the production of polyfurandicarboxylates, which are biodegradable polyesters expected to substitute their classical counterparts derived from fossil resources. It may be produced from bio-based 5-hydroxymethylfurfural or 5-methoxymethylfurfural, both obtained by the acidic dehydration of biomass-derived fructose. 5-Methoxymethylfurfural, which is produced in the presence of methanol, generates less by-products and exhibits better storage stability than 5-hydroxymethylfurfural being, therefore, the industrial substrate of choice.

Stepwise Hydrogen Atom and Proton Transfers in Dioxygen Reduction by Aryl-Alcohol Oxidase.

The mechanism of dioxygen reduction by the flavoenzyme aryl-alcohol oxidase was investigated with kinetic isotope, viscosity, and pL (pH/pD) effects in rapid kinetics experiments by stopped-flow spectrophotometry of the oxidative half-reaction of the enzyme. Double mixing of the enzyme in a stopped-flow spectrophotometer with [α-H]- p-methoxybenzyl alcohol and oxygen at varying aging times established a slow rate constant of 0.0023 s for the wash-out of the D atom from the N5 atom of the reduced flavin.

Protein dynamics promote hydride tunnelling in substrate oxidation by aryl-alcohol oxidase.

The temperature dependence of hydride transfer from the substrate to the N5 of the FAD cofactor during the reductive half-reaction of Pleurotus eryngii aryl-alcohol oxidase (AAO) is assessed here. Kinetic isotope effects on both the pre-steady state reduction of the enzyme and its steady-state kinetics, with differently deuterated substrates, suggest an environmentally-coupled quantum-mechanical tunnelling process. Moreover, those kinetic data, along with the crystallographic structure of the enzyme in complex with a substrate analogue, indicate that AAO shows a pre-organized active site that would only require the approaching of the hydride donor and acceptor for the tunnelled transfer to take place.

Relations between Sensorimotor Integration and Speech Disorders in Parkinson's Disease.

Background: Sensorimotor integration mechanisms can be affected by many factors, among which are those involving neuromuscular disorders. Parkinson's disease (PD) is characterized by well-known motor symptoms, among which lately have been included motor speech deficits. Measurement of the acoustic startle reflex (ASR) and its modulations (prepulse inhibition and prepulse facilitation, PPI and PPF respectively) represent a simple and quantifiable tool to assess sensorimotor function.

Voice Markers of Lexical Access in Mild Cognitive Impairment and Alzheimer's Disease.

Background: Recent studies have identified the correlation between dementia and certain vocal features, such as voice and speech changes. Vocal features may act as early markers of Alzheimer's disease (AD). Despite being present in non-pathological senescence and Mild Cognitive Impairment, especially in its amnesic subtype (aMCI), these voice- and speech-related symptoms are the first signs of AD.

Morphological correlates of sex differences in acoustic startle response and prepulse inhibition through projections from locus coeruleus to cochlear root neurons.

The noradrenergic locus coeruleus (LC) plays an important role in the promotion and maintenance of arousal and alertness. Our group recently described coerulean projections to cochlear root neurons (CRNs), the first relay of the primary acoustic startle reflex (ASR) circuit. However, the role of the LC in the ASR and its modulation, prepulse inhibition (PPI), is not clear.

Speech rhythm alterations in Spanish-speaking individuals with Alzheimer's disease.

Rhythm is the speech property related to the temporal organization of sounds. Considerable evidence is now available for suggesting that dementia of Alzheimer's type is associated with impairments in speech rhythm. The aim of this study is to assess the use of an automatic computerized system for measuring speech rhythm characteristics in an oral reading task performed by 45 patients with Alzheimer's disease (AD) compared with those same characteristics among 82 healthy older adults without a diagnosis of dementia, and matched by age, sex and cultural background.

A survey of genes encoding H2O2-producing GMC oxidoreductases in 10 Polyporales genomes.

The genomes of three representative Polyporales (Bjerkandera adusta, Phlebia brevispora and a member of the Ganoderma lucidum complex) recently were sequenced to expand our knowledge on the diversity and distribution of genes involved in degradation of plant polymers in this Basidiomycota order, which includes most wood-rotting fungi. Oxidases, including members of the glucose-methanol-choline (GMC) oxidoreductase superfamily, play a central role in the above degradative process because they generate extracellular H2O2 acting as the ultimate oxidizer in both white-rot and brown-rot decay. The survey was completed by analyzing the GMC genes in the available genomes of seven more species to cover the four Polyporales clades.

Aromatic stacking interactions govern catalysis in aryl-alcohol oxidase.

Aryl-alcohol oxidase (AAO, EC 1.1.3.

Improvement of encoding and retrieval in normal and pathological aging with word-picture paradigm.

Objectives: During the aging process, there is a progressive deficit in the encoding of new information and its retrieval. Different strategies are used in order to maintain, optimize or diminish these deficits in people with and without dementia. One of the classic techniques is paired-associate learning (PAL), which is based on improving the encoding of memories, but it has yet to be used to its full potential in people with dementia.