title: Cystathioninuria and homocystinuria.
abstract: Three circumstances prompted us to reexamine the relationship between abnormal cystathionine accumulation and possible homocystinuria resulting from this condition: (a) discovery of an infant girl with apparently alternating massive cystathioninuria and homocystinuria; (b) the presence of homocystinuria in some, but not all, previously reported cases of cystathioninuria probably due to gamma-cystathionine deficiency; and (c) the recent demonstration that mammalian cystathionine beta-synthase can cleave cystathionine to homocysteine. The following conclusions were reached: (a) Homocystine may arise as a result of bacterial contamination of a urine sample initially containing cystathionine, but not homocystine. (b) After a methionine load, a cystathioninuric patient may excrete readily detected amounts of homocystine. (c) However, homocystinuria is not a necessary concomitant of even massive cystathioninuria. These findings and some of their implications are briefly discussed.
mesh_terms: D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood / Q000652:urine*; D001419:Bacteria / Q000378:metabolism; D003540:Cystathionine / Q000652:urine*; D005260:Female; D006712:Homocystinuria / Q000652:urine*; D006801:Humans; D007223:Infant; D013048:Specimen Handling; D013943:Thymol; D014050:Toluene; D014556:Urine
chemical_list: D003540:Cystathionine; D014050:Toluene; D013943:Thymol