Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

BACKGROUND The urea cycle converts amino acids to urea and is excreted by the kidneys. Ornithine carbamoyltransferase (OTC) deficiency is a rare X-linked urea cycle disorder which results in hyperammonemia. Diagnosis is made based on a clinical presentation of poor feeding, hypotonia, biochemical profile, and genetic testing. Another genetic cause for hyperammonemia is hyperammonia hyperinsulinemia (HAHI) syndrome. A mutation coding for glutamate dehydrogenase (GDH) results in increased alpha-keto glutarate and ATP, triggering the secretion of pancreatic insulin. However, unlike OTC deficiency, these patients are asymptomatic but do have symptoms of hypoglycemia. The purpose of this article is to present the case of a 66-year-old woman with an unusual late-onset of OTC deficiency compounded with an underlying HAHI syndrome with co-disease management. CASE REPORT A 66-year-old female with a history significant for transient ischemic attack (TIA) and urea cycle disorder was admitted for new adverse symptoms. Further evaluation revealed hyperammonemia and hypoglycemia. Despite standard previous treatment for her underlying urea cycle disorder, high ammonia levels and hypoglycemia persisted. The contradicting values with continued hypoglycemia regardless of dextrose treatment was suspicious for underlying HAHI. Further genetic testing during her admission revealed a deletion in GLUD-1 gene concurrent with diagnosis of HAHI. After co-diagnosis was established, effective management required medications for both disorders in concordance with dietary restriction. CONCLUSIONS This is an extremely rare case of OTC deficiency, with a vague presentation in an elderly female. Exploring compounding genetic disorders in the presence of one that is already established and early recognition are crucial for prompt diagnosis and management.
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PMID:Management of Ornithine Carbamoyltransferase Deficiency with Underlying Hyperammonia Hyperinsulinemia Syndrome. 3133 45

Short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD), encoded by the HADH gene, is a ubiquitously expressed mitochondrial enzyme involved in fatty acid oxidation. This protein also plays a role in insulin secretion as recessive HADH mutations cause congenital hyperinsulinism of infancy (CHI) via loss of an inhibitory interaction with glutamate dehydrogenase (GDH). Here, we present a functional evaluation of 16 SCHAD missense variants identified either in CHI patients or by high-throughput sequencing projects in various populations. To avoid interactions with endogenously produced SCHAD protein, we assessed protein stability, subcellular localization, and GDH interaction in a SCHAD knockout HEK293 cell line constructed by CRISPR-Cas9 methodology. We also established methods for efficient SCHAD expression and purification in E. coli, and tested enzymatic activity of the variants. Our analyses showed that rare variants of unknown significance identified in populations generally had similar properties as normal SCHAD. However, the CHI-associated variants p.Gly34Arg, p.Ile184Phe, p.Pro258Leu, and p.Gly303Ser were unstable with low protein levels detectable when expressed in HEK293 cells. Moreover, CHI variants p.Lys136Glu, p.His170Arg, and p.Met188Val presented normal protein levels but displayed clearly impaired enzymatic activity in vitro, and their interaction with GDH appeared reduced. Our results suggest that pathogenic missense variants of SCHAD either make the protein target of a post-translational quality control system or can impair the function of SCHAD without influencing its steady-state protein level. We did not find any evidence that rare SCHAD missense variants observed only in the general population and not in CHI patients are functionally affected.
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PMID:Functional evaluation of 16 SCHAD missense variants: Only amino acid substitutions causing congenital hyperinsulinism of infancy lead to loss-of-function phenotypes in vitro. 3287 54


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