DypB peroxidase for aflatoxin removal: New insights into the toxin degradation process.

Aflatoxin B1 (AFB1) is one of the most potent carcinogens and a widespread food and feed contaminant. As for other toxins, many efforts are devoted to find efficient and environmentally-friendly methods to degrade AFB1, such as enzymatic treatments, thus improving the safety of food and feed products. In this regard, the dye decolorizing peroxidase of type B (DypB) can efficiently degrade AFB1. The molecular mechanism, which is required to drive protein optimization in view of the usage of DypB as a mycotoxin reduction agent in large scale application, is unknown. Here, we focused on the role of four DypB residues in the degradation of AFB1 by alanine-scanning (residues 156, 215, 239 and 246), which were identified from biochemical assays to be kinetically relevant for the degradation. As a result of DypB degradation, AFB1 is converted into four products. Interestingly, the relative abundancy of these products depends on the replaced residues. Molecular dynamics simulations were used to investigate the role of these residues in the binding step between protein and manganese, a metal ion which is expected to be involved in the degradation process. We found that the size of the haem pocket as well as conformational changes in the protein structure could play a role in determining the kinetics of AFB1 removal and, consequently, guide the process towards specific degradation products.

Ménière's disease and anxiety disorders.

Diagnosis of Menière's Disease is based upon the wellknown labyrinthic syndrome (hypoacusia, tinnitus and dizziness) which manifests with the typical abscessual, recurrent and unforeseeable course. Many Menière patients also report panic attacks, agoraphobia and anxiety which make evaluation of labyrinthic symptoms difficult, affect the onset and maintenance of vestibular compensation and require specific treatments which are very different from those for the control of endolymphatic hydrops. In order to analyse the nature and the meaning of the association of the vestibular and psychiatric symptoms, a comparison has been made between patients presenting Menière's disease, and a group of patients with dizziness resulting from other vestibular diseases. Socio-demographic data were collected and anxiety tests were used to evaluate, the depression and phobia. An interview ad hoc was also programmed for the psychiatric diagnosis. A previous psychiatric history, age, sex, marital status as well as education appear to have a variable effect upon the onset and evolution of panic-phobic symptoms, following onset of Menière's disease. These conclusions, which require confirmation with further studies, allow early characterisation of Menière's disease patients of great predictive usefulness as far as concerns the development of psychiatric sequelae of a panic-phobic nature. This evolution is far more frequent in females being enhanced by middle age, low level of education, long-standing Menière's disease and large number of attacks of dizziness. Onset of panic-phobic attacks is more rare in males in whom the condition is associated with young age, high level of education, lack of setting up of a family nucleus with children.