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Stabilization of the thermolabile variant S113L of carnitine palmitoyltransferase II.

ABSTRACT: OBJECTIVE:Muscle carnitine palmitoyltransferase (CPT) II deficiency, the most common defect of lipid metabolism in muscle, is characterized by attacks of myoglobinuria without persistent muscle weakness. METHODS:His6-N-hCPT2 (wild-type) and His6-N-hCPT2/S113L (variant) were produced recombinantly in prokaryotic host and characterized according to their functional and regulatory properties. RESULTS:The wild-type and the variant S113L showed the same enzymatic activity and thermostability at 30°C. The mutated enzyme, however, revealed an abnormal thermal destabilization at 40°C and 45°C. This was consistent with an increased flexibility (B-factor) of the variant at 40°C compared with that of the wild-type shown by molecular dynamics analysis. Preincubation of the enzymes with l-carnitine and acyl-l-carnitines containing more than 10 carbons in the acyl side-chain stabilized the mutated enzyme against thermal inactivation. In contrast, palmitoyl-CoA destabilized both enzymes. CONCLUSIONS:The problems in CPT II deficiency originating from the S113L mutation are not caused by the loss of catalytically active enzyme. They might be at least partially related to an impaired thermal stability of the protein. The lower thermodynamic stability of the variant might explain why fever and prolonged exertion provoke attacks of myoglobinuria in CPT II deficiency. The stabilization by acyl-l-carnitines might provide the basis for possible preventive therapy of CPT II deficiency.

SUBMITTER: Motlagh L

PROVIDER: S-EPMC4830186 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Stabilization of the thermolabile variant S113L of carnitine palmitoyltransferase II.

Motlagh Leila L Golbik Ralph R Sippl Wolfgang W Zierz Stephan S

Neurology. Genetics 20160225 2

<h4>Objective</h4>Muscle carnitine palmitoyltransferase (CPT) II deficiency, the most common defect of lipid metabolism in muscle, is characterized by attacks of myoglobinuria without persistent muscle weakness.<h4>Methods</h4>His6-N-hCPT2 (wild-type) and His6-N-hCPT2/S113L (variant) were produced recombinantly in prokaryotic host and characterized according to their functional and regulatory properties.<h4>Results</h4>The wild-type and the variant S113L showed the same enzymatic activity and th ...[more]

PMID: 27123472

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Project description:Aim:In serious heatstroke, elevated body temperature (>40°C) is considered the main cause of illness. Mitochondrial carnitine palmitoyltransferase II (CPT II) plays an important role in adenosine triphosphate (ATP) generation from long-chain fatty acids, and its thermolabile phenotype of CPT2 polymorphisms leads to ATP production loss under high fever. Whether by heatstroke or influenza, high fever suppresses mitochondrial ATP production in patients with the thermolabile phenotype of CPT2 polymorphisms. We investigated the relation between CPT2 polymorphism and severity of heatstroke with a body temperature of over 40°C. Methods:We analyzed blood chemistry test results, Japanese Association for Acute Medicine Disseminated Intravascular Coagulation (JAAM DIC), Acute Physiologic and Chronic Health Evaluation II, and Sequential Organ Failure Assessment (SOFA) scores, and CPT2 polymorphisms in 24 consecutive patients with severe heatstroke at two university hospitals. Results:Eleven patients carried thermolabile CPT II variants (rs2229291; c.1055T?G [p.Phe352Cys]) (F352C), and the genotype frequency was greater in heatstroke patients than in healthy volunteers. There was no significant difference in body temperature or blood chemistry data at emergency room arrival between patients with and without the CPT II variants. However, hospital days were longer and initial antithrombin activity was significantly lower in the variant group, suggesting a possible link with early phase vascular endothelial cell dysfunction. The JAAM DIC diagnostic criteria and SOFA scores were also higher in the group. There were no differences in the serum albumin, serum creatine kinase, and fibrin degradation product levels, and platelet counts. Conclusions:In addition to known risks (e.g., environmental temperature and old age), the CPT II polymorphism [F352C] can be a predisposing genetic risk factor for serious heatstroke with organ disfunction, and lower antithrombin activity.

Project description:Carnitine palmitoyltransferase (CPT) catalyzes the transfer of long- and medium-chain fatty acids from cytoplasm into mitochondria, where oxidation of fatty acids takes place. Deficiency of CPT enzyme is associated with rare diseases of fatty acid metabolism. CPT is present in two subforms: CPT I at the outer mitochondrial membrane and carnitine palmitoyltransferase II (CPT II) inside the mitochondria. Deficiency of CPT II results in the most common inherited disorder of long-chain fatty acid oxidation affecting skeletal muscle. There is a lethal neonatal form, a severe infantile hepato-cardio-muscular form, and a rather mild myopathic form characterized by exercise-induced myalgia, weakness, and myoglobinuria. Total CPT activity (CPT I + CPT II) in muscles of CPT II-deficient patients is generally normal. Nevertheless, in some patients, not detectable to reduced total activities are also reported. CPT II protein is also shown in normal concentration in patients with normal CPT enzymatic activity. However, residual CPT II shows abnormal inhibition sensitivity towards malonyl-CoA, Triton X-100 and fatty acid metabolites in patients. Genetic studies have identified a common p.Ser113Leu mutation in the muscle form along with around 100 different rare mutations. The biochemical consequences of these mutations have been controversial. Hypotheses include lack of enzymatically active protein, partial enzyme deficiency and abnormally regulated enzyme. The recombinant enzyme experiments that we recently conducted have shown that CPT II enzyme is extremely thermoliable and is abnormally inhibited by different emulsifiers and detergents such as malonyl-CoA, palmitoyl-CoA, palmitoylcarnitine, Tween 20 and Triton X-100. Here, we present a conceptual overview on CPT II deficiency based on our own findings and on results from other studies addressing clinical, biochemical, histological, immunohistological and genetic aspects, as well as recent advancements in diagnosis and therapeutic strategies in this disorder.

Project description:IntroductionThe occurrence of repeated and progressive rhabdomyolysis is rare in clinical settings, particularly in adults. The pathogenesis of rhabdomyolysis is often overlooked due to its rapid recovery. Carnitine palmitoyltransferase (CPT) II deficiency could be a rare etiology of repetitive nontraumatic rhabdomyolysis, and several mutations of CPT II have been reported.Patient concernsA 41-year-old man presented with high fever, general malaise, myalgia, dyspnea, and dark-colored urine, and then progressed to anuria. In the past 15 years, he experienced dark-colored urine twice due to exercise and high fever. Physical examination revealed oliguria, suppurated tonsils, poor hemoglobin saturation, alert consciousness, normal neurological signs and reflexes, hypertension, and tachypnea. Laboratory investigations showed positive test results for inflammation, high serum myogenic enzyme levels, and evidence of acute kidney injury (AKI).DiagnosesInvestigations revealed an extremely high serum myogenic enzyme levels and impaired renal function with serum creatinine level of 510 μmol/L, consistent with the diagnosis of rhabdomyolysis, AKI stage 3, and acute respiratory distress syndrome. High levels of acylcarnitine in the serum confirmed the diagnosis of CPT II deficiency. In addition, whole exome sequencing (WES) was conducted in the patient and his mother.InterventionsIntubation, ventilator support, and hemodialysis were the major therapeutic interventions at the peak of disease progression. He was then administered valsartan tablets at a dosage of 80 mg per day and L-carnitine supplements.OutcomesWES conducted in the patient and his mother revealed 2 novel mutations of CPT II (c.482G>A and c.1493G>T) in this patient. The patient recovered from the severe AKI but the renal function remained impaired at chronic kidney disease stage 3a.ConclusionThus, gene examination can help to understand the etiology of repetitive nontraumatic rhabdomyolysis. Accurate diagnosis can be beneficial for providing an individualized treatment for patients with repeated and progressive rhabdomyolysis.

Dataset Information

Stabilization of the thermolabile variant S113L of carnitine palmitoyltransferase II.

Publications

Stabilization of the thermolabile variant S113L of carnitine palmitoyltransferase II.

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