A 'random steady-state' model for the pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase enzyme complexes.

The multienzyme complexes, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, involved in the central metabolism of Escherichia coli consist of multiple copies of three different enzymes, E1, E2 and E3, that cooperate to channel substrate intermediates between their active sites. The E2 components form the core of the complex, while a mixture of E1 and E3 components binds to the core. We present a random steady-state model to describe catalysis by such multienzyme complexes. At a fast time scale, the model describes the enzyme catalytic mechanisms of substrate channeling at a steady state, by polynomially approximating the analytic solution of a biochemical master equation. At a slower time scale, the structural organization of the different enzymes in the complex and their random binding/unbinding to the core is modeled using methods from equilibrium statistical mechanics. Biologically, the model describes the optimization of catalytic activity by substrate sharing over the entire enzyme complex. The resulting enzymatic models illustrate the random steady state (RSS) for modeling multienzyme complexes in metabolic pathways.

[Congenital bronchobiliary fistula: a case report]. / Fistule bronchobiliaire congénitale : à propos d'une observation.

Congenital bronchobiliary fistulas (CBBF) are rare developmental anomalies. We report a case of a 6-day-old newborn who presented with respiratory distress and bilioptysis, originally involving a meconium aspiration syndrome. The diagnosis was confirmed by bronchoscopy. Surgery was performed at the age of 26 days and the newborn died the following day. Operative opacification showed communication between the carina and the biliary system. We review the clinical characteristics of CBBF and the value of early diagnosis and surgical treatment to prevent pulmonary complications due to bile salts.

[Caffey disease (infantile cortical hyperostosis)]. / La maladie de Caffey.

CASE REPORT: A case of infantile cortical hyperostosis is reported in a 4-month old infant. The disease was revealed by changes in behavior and swelling of bones. X-rays of bones led to the correct diagnosis. The spontaneous outcome was favorable. CONCLUSION: The clinical, biological and radiological aspects of this disease are described in order to recognize it early.