A combined computational and experimental study on selective flucloxacillin hydroxylation by cytochrome P450 BM3 variants.

The 5'-hydroxymethyl metabolite of the penicillin based antibiotic flucloxacillin (FLX) is considered to be involved in bile duct damage occurring in a small number of patients. Because 5'-hydroxymethyl FLX is difficult to obtain by organic synthesis, biosynthesis using highly active and regioselective biocatalysts would be an alternative approach. By screening an in-house library of Cytochrome P450 (CYP) BM3 mutants, mutant M11 L437E was identified as a regioselective enzyme with relatively high activity in production of 5'-hydroxymethyl FLX as was confirmed by mass spectrometry and NMR. In contrast, incubation of M11 L437E and other mutants with oxacillin (OX, which differs from FLX by a lack of aromatic halogens) resulted in formation of two metabolites. In addition to 5'-hydroxymethyl OX we identified a product resulting from aromatic hydroxylation. In silico studies of both FLX and OX with three CYP BM3 mutants revealed substrate binding poses allowing for 5'-methyl hydroxylation, as well as binding poses with the aromatic moiety in the vicinity of the heme iron for which the corresponding product of aromatic hydroxylation was not observed for FLX. Supported by the (differences in) experimentally determined ratios of product formation for OX hydroxylation by M11 and its L437A variant and M11 L437E, Molecular Dynamics simulations suggest that the preference of mutant M11 L437E to bind FLX in its catalytically active pose over the other binding orientation contributes to its biocatalytic activity, highlighting the benefit of studying effects of active-site mutations on possible alternative enzyme-substrate binding poses in protein engineering.

The successful non-invasive management of pulmonary thromboembolism in a child with acute lymphoblastic leukemia.

In childhood, pulmonary thromboembolism (PTE) is an uncommonbut potentially life-threatening disease. The greater numbers of venous thromboembolism (VTE) are complications of underlying risk factors such as malignancies, chemotherapy (L-asparaginase), and central venous catheter. We report a patient with acute lymphoblastic leukemia and PTE, who presented with near-syncope, and was successfully treated with low molecular weight heparin and calcium channel blockers.

Éxito en el manejo no invasivo de la tromboembolia pulmonar en un niño con leucemia linfocítica aguda / The successful non-invasive management of pulmonary thromboembolism in a child with acute lymphoblastic leukemia

Durante la niñez, la tromboembolia pulmonar (TEP) es una afección poco frecuente, aunque potencialmente mortal. El mayor número de episodios de tromboemblia venosa (TEV) es resultado de complicaciones de factores de riesgo subyacentes, tales como tumores malignos, quimioterapia (L-asparaginasa) y colocación de un catéter venoso central. Presentamos el caso de un paciente con leucemia linfocítica aguda y TEP que tuvo un presíncope y fue tratado satisfactoriamente con heparina de bajo peso molecular y antagonistas del calcio.

In childhood, pulmonary thromboembolism (PTE) is an uncommonbut potentially life-threatening disease. The greater numbers of venous thromboembolism (VTE) are complications of underlying risk factors such as malignancies, chemotherapy (L-asparaginase), and central venous catheter. We report a patient with acute lymphoblastic leukemia and PTE, who presented with near-syncope, and was successfully treated with low molecular weight heparin and calcium channel blockers.