RESUMO
(1) L-Alanine dehydrogenase from Bacillus cereus was purified by a two-step chromatographic procedure involving Cibacron-Blue 3G-A Sepharose 4B-CL, and Sepharose 6B-CL, and immobilized on CNBr-activated Sepharose 4B. (2) Following immobilization via two of the six subunits, L-alanine dehydrogenase retained 66% of the specific activity of the soluble enzyme. The affinity of the immobilized enzyme for NH4+, pyruvate and L-alanine, was not different to that of the soluble form. The Km of the Sepharose-bound L-alanine dehydrogenase for pyridine coenzymes was 6-8-times higher than in the soluble case. (3) The stability of L-alanine dehydrogenase towards urea or thermal denaturation was increased by immobilization. (4) The incubation at 37 degrees C for 24 h of the immobilized L-alanine dehydrogenase with 3 M NH4Cl/NH4OH buffer (pH 9) released 70% of the enzyme. The specific activity and the affinity of the 'solubilized' L-alanine dehydrogenase for the pyridine coenzymes was the same as that obtained with the original, soluble L-alanine dehydrogenase.
Assuntos
Aminoácido Oxirredutases/metabolismo , Bacillus cereus/enzimologia , Alanina Desidrogenase , Sítios de Ligação , Enzimas Imobilizadas/metabolismo , Cinética , Desnaturação Proteica , Sefarose , Solubilidade , UreiaRESUMO
Serologic investigations carried out in 254 children admitted to a Clinic for Children for respiratory diseases, established a diagnosis of infection with parainfluenza virus in 19.2% of cases. The predominant age-group affected was 7--12 months and 0--6 months; the causative agent in most cases was parainfluenza type 3, followed by type 2 and then type 1. The role of parainfluenza viruses in the aetiology of laryngotracheobronchiectasis was confirmed, as well as their participation in the aetiology of pneumonia in infants. The results also showed the wide circulation of parainfluenza viruses in children and their outstanding contribution to respiratory diseases among hospitalized children within a period of four years.
