alpha-chymotrypsin and Mitochondrial-Diseases

Exocrine pancreatic insufficiency in children can lead to lifelong complications related to malnutrition and poor growth. The clinical presentation can be subtle in the early stages of insufficiency as the large functional capacity of the pancreas is gradually lost. The pediatrician plays a crucial role in the early identification of these children to ensure a timely referral so that a diagnosis can be made and therapy initiated. Early nutritional therapy allows for prevention and correction of deficiencies, which leads to improved outcomes and survival. When insufficiency is suspected, the workup should start with an indirect test of exocrine pancreatic function, such as fecal elastase, to establish the diagnosis. Once a diagnosis is established, further testing to delineate the etiology should be pursued, with cystic fibrosis being high on the differential list and assessed for with a sweat test. Assessment of anthropometry at every visit is key, as is monitoring of laboratory parameters and physical examination findings that are suggestive of malabsorption and malnutrition. The mainstay of management is administration of exogenous pancreatic enzymes to facilitate digestion and absorption. [Pediatr Ann. 2019;48(11):e441-e447.].

Topics: Acyl-CoA Dehydrogenase, Long-Chain; Anus, Imperforate; Child; Child Nutrition Disorders; Chymotrypsin; Congenital Bone Marrow Failure Syndromes; Cystic Fibrosis; Dietary Fats; Ectodermal Dysplasia; Enzyme Replacement Therapy; Exocrine Pancreatic Insufficiency; Feces; Growth Disorders; Hearing Loss, Sensorineural; Humans; Hypothyroidism; Intellectual Disability; Lipid Metabolism, Inborn Errors; Mitochondrial Diseases; Muscular Diseases; Nose; Nutrition Assessment; Pancreas; Pancreatic Diseases; Pancreatic Elastase; Pancreatic Function Tests; Pancreatitis, Chronic; Shwachman-Diamond Syndrome; Steatorrhea; Trypsinogen

Mitochondrial complex I (NADH:ubiquinone oxidoreductase) undergoes reversible deactivation upon incubation at 30-37 degrees C. The active/deactive transition could play an important role in the regulation of complex I activity. It has been suggested recently that complex I may become modified by S-nitrosation under pathological conditions during hypoxia or when the nitric oxide:oxygen ratio increases. Apparently, a specific cysteine becomes accessible to chemical modification only in the deactive form of the enzyme. By selective fluorescence labeling and proteomic analysis, we have identified this residue as cysteine-39 of the mitochondrially encoded ND3 subunit of bovine heart mitochondria. Cysteine-39 is located in a loop connecting the first and second transmembrane helix of this highly hydrophobic subunit. We propose that this loop connects the ND3 subunit of the membrane arm with the PSST subunit of the peripheral arm of complex I, placing it in a region that is known to be critical for the catalytic mechanism of complex I. In fact, mutations in three positions of the loop were previously reported to cause Leigh syndrome with and without dystonia or progressive mitochondrial disease.

Topics: Animals; Catalysis; Cattle; Chymotrypsin; Cysteine; Electron Transport Complex I; Electrophoresis, Polyacrylamide Gel; Fluorescent Dyes; Mass Spectrometry; Mitochondrial Diseases; Models, Biological; Myocardium; Nitric Oxide; Oxygen; Proteomics

We used electron microscopy to examine the structure of human DNA pol gamma, the heterotrimeric mtDNA replicase implicated in certain mitochondrial diseases and aging models. Separate analysis of negatively stained preparations of the catalytic subunit, pol gammaA, and of the holoenzyme including a dimeric accessory factor, pol gammaB(2), permitted unambiguous identification of the position of the accessory factor within the holoenzyme. The model explains protection of a partial chymotryptic cleavage site after residue L(549) of pol gammaA upon binding of the accessory subunit. This interaction region is near residue 467 of pol gammaA, where a disease-related mutation has been reported to impair binding of the B subunit. One pol gammaB subunit dominates contacts with the catalytic subunit, while the second B subunit is largely exposed to solvent. A model for pol gamma is discussed that considers the effects of known mutations in the accessory subunit and the interaction of the enzyme with DNA.

Topics: Aging; Catalytic Domain; Chymotrypsin; DNA Polymerase gamma; DNA-Directed DNA Polymerase; Humans; Microscopy, Electron, Transmission; Mitochondrial Diseases; Models, Biological; Models, Molecular; Protein Structure, Tertiary; Structure-Activity Relationship