AMINOACIDOPATHIES – CLASSIFICATION AND DIAGNOSIS Dr. Hariharan, II yr MD biochemistry Moderator - Dr.Ragavendran, Professor, Dept of pediatrics Co-ordinator- Dr. Ashok kumar, MD, DLO, Assistant Professor, Dept of Biochemistry

History Garrod – alkaptonuria, benign pentosuria, albinism, cystinuria Følling’s -phenylketonuria (PKU) in 1934 Harry Harris-1955-starch gel electrophoresis- demonstrated of a large number of protein polymorphisms in humans discovery of PKU sparked the search for other clinically significant inborn errors of metabolism> 500 disorders

A ABC D negative EF Apoenzyme + cofactor What can go wrong?

Incidence of aminoacidurias Tyrosinemias1.5 : 1000 PKU1 : 10,000 Histidinemia1 : 10,000 Urea cycle defects1 : 20,000 Methyl malonic aciduria1 : 20,000 Maple Syrup Urine Disease1 : 100,000 Alkaptonuria1 : 250,000

Inheritance

Disorders of amino acid metabolism Defects in aminoacid catabolism Urea cycle defects Glycine Nonketotic hyper glycinemia, Primary hyper oxaluria S containing aminoacids cystinuria, homo cystinuria, cysta thioninuria Branched chain a.a MSUD Aromatic a.a PKU, alkaptonuria, hyper tyrosinemias Defects in aminoacid membrane transport Cystinuria Hartnup’s disease

Urea cycle defects OrnithineCitrulline Argino succinate Arginine NH3 + H20 + CO2 Carbamoyl phosphate Hyperammonemia I Hyperammonemia II OTC Urea citrullinemia Argino succinic aciduria

Branched chain aminoacidurias Leucine, isoleucine, valine Corresponding Ketoacids Isobutyryl coA Methyl butryl coA Propionyl coA Isovaleryl coA Methyl crotonyl coA Isovaleryl coA dehydrogenase Alpha ketoacid dehydrogenase

Homocystinurias Homocystinuria 1 Methionine S-adenosyl methionine S adenosyl homocysteine Homocysteine Cystathionine Homocystinuria 3 Homocystinuria 2 N5-N10 MTHF transferase MTHFR

Phenylalanine and tyrosine Phenyl alanineTyrosine P-hydroxy phenyl pyruvic acid Homogentisic acidMaleyl acetoacetateFumaryl acetoacetate Acetoacetate and fumarate Tyrosinemia 2 Tyrosinemia 1 Alkaptonuria PKU hydroxylase Amino transferase Hydrolase

Laboratory investigation Blood – Electrolytes, glucose, ammonia URINE- – Ferric chloride test- alkaptonuria – Cyanide nitroprusside -S- – DNPH-MSUD – Benedict’s test -alkaptonuria Thin layer chromatography Tandem mass spectrometry

Confirmatory tests PKU- plasma phenyl alanine levels, urinary metabolites Tyrosinemias-plasma tyrosine levels, urine- succinyl acetone Homocystinurias- increased plasma methionine & homocysteine. Low cystine MSUD- increased leucine, isoleucine, valine Urea cycle defects- ammonia, glutamine, alanine, other aminoacids

Collection of urine sample

Screening in newborn Guthrie’s test- earliest Various procedures in varying countries

References Vasudevan- textbook of biochemistry A clinical guide to inherited metabolic disorders- Clarke Pubmed.com Wikipedia.org