The role of the C8 proton of ATP in the regulation of phosphoryl transfer within kinases and synthetases

<p>Abstract</p> <p>Background</p> <p>The kinome comprises functionally diverse enzymes, with the current classification indicating very little about the extent of conserved regulatory mechanisms associated with phosphoryl transfer. The apparent <it>K</it>_mof the kinases ranges from less than 0.4 μM to in excess of 1000 μM for ATP. It is not known how this diverse range of enzymes mechanistically achieves the regulation of catalysis via an affinity range for ATP varying by three-orders of magnitude.</p> <p>Results</p> <p>We have demonstrated a previously undiscovered mechanism in kinase and synthetase enzymes where the overall rate of reaction is regulated via the C8-H of ATP. Using ATP deuterated at the C8 position (C8D-ATP) as a molecular probe it was shown that the C8-H plays a direct role in the regulation of the overall rate of reaction in a range of kinase and synthetase enzymes. Using comparative studies on the effect of the concentration of ATP and C8D-ATP on the activity of the enzymes we demonstrated that not only did C8D-ATP give a kinetic isotope effect (KIE) but the KIE's obtained are clearly not secondary KIE effects as the magnitude of the KIE in all cases was at least 2 fold and in most cases in excess of 7 fold.</p> <p>Conclusions</p> <p>Kinase and synthetase enzymes utilise C8D-ATP in preference to non-deuterated ATP. The KIE obtained at low ATP concentrations is clearly a primary KIE demonstrating strong evidence that the bond to the isotopically substituted hydrogen is being broken. The effect of the ATP concentration profile on the KIE was used to develop a model whereby the C8H of ATP plays a role in the overall regulation of phosphoryl transfer. This role of the C8H of ATP in the regulation of substrate binding appears to have been conserved in all kinase and synthetase enzymes as one of the mechanisms associated with binding of ATP. The induction of the C8H to be labile by active site residues coordinated to the ATP purine ring may play a significant role in explaining the broad range of <it>K</it>_massociated with kinase enzymes.</p

Examining the added value of the use of an experiment design tool among secondary students when experimenting with a virtual lab

International audienc

A importância do potássio e da alimentação na regulação da pressão arterial

Publicação no âmbito do Programa Nacional para a Promoção da Alimentação Saudável da DGS

Sinonasal adenocarcinomas: experience of Lisbon Oncology Institute between 2000 and 2014

Objetivos: Analisar dados demográficos, apresentação clínica, fatores de risco, opções terapêuticas e sobrevida de doentes com adenocarcinoma nasossinusal. Material e Métodos: Estudo retrospetivo de doentes com Adenocarcinoma Nasossinusal tratados entre 2000 e 2014, no IPOFGL. Resultados: Identificamos 33 doentes com diagnóstico de Adenocarcinoma. A idade média foi de 65.6 anos. A terapêutica mais comum foi cirurgia com radioterapia adjuvante. A sobrevida global e livre de doença aos 3 anos foi de 57.6% e 40.5%. A invasão do seio esfenoidal (p=0.038) e da base do crânio (p=0.003) influenciaram a sobrevida global. O desenvolvimento de metástases à distância teve impacto sobre a sobrevida livre de doença (p=0.01). Conclusões: Os Adenocarcinomas são tumores raros. A excisão da lesão toma um papel determinante no tratamento dos doentes. Na nossa amostra, a invasão do seio esfenoidal, da base do crânio e o desenvolvimento de metástases à distância estão associados a um pior prognóstico.Objective: To analyze treatment outcomes, including overall and disease-free survival rates, of patients with sinonasal adenocarcinomas. Methods: Retrospective study of patients with sinonasal adenocarcinoma treated in IPOFGL between 2000 and 2014. Results: We identified 33 patients; 17 were women and 16 men. Average age at diagnosis was 65.6 years and median follow-up was 39 months. Ethmoid sinus was the most frequent location; 51% presented at AJCC stage IV. Surgery with adjuvant radiotherapy was used in 70%. Overall survival at 36 months was 57.6%, with 40.5% disease-free survival. Recurrence was caused by local failure in majority of cases. Survival was decreased significantly in patients with sphenoid sinus involvement (p=0.038), skull base invasion (p=0.003) and recurrence metastatic disease (p<0.05). Conclusions: Complete surgical removal with postoperative radiotherapy remains the standard treatment modality. Sphenoid sinus and skull base invasion, and development of distant metastasis portend for poor prognosis

Assessing chronic wasting disease risk in Portugal

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