title: [Enzyme analysis of isolated mitochondrial respiratory chain complex III deficiency].
abstract: OBJECTIVE
  To study the clinical and enzymological characteristics of the children with mitochondrial respiratory chain complex III deficiency.
  
  
  METHODS
  The clinical manifestations of five patients (3 males, 2 females) were summarized. Spectrophotometric assay was used for the analysis of respiratory chain complex I to V enzyme activity in peripheral blood leukocytes, after obtaining venous blood.
  
  
  RESULTS
  (1) Five patients were hospitalized at the age of 1 month to 15 years. Three patients had Leigh syndrome with progressive motor developmental delay or regression and weakness. One had severe liver damage and intrahepatic cholestasis. One presented muscle weakness. (2) Deficient complex I + III activity was identified in five patients. Their complex I + III activities in peripheral blood leukocytes were 3.0 to 14.2 nmol/min per mg mitochondrial protein (control: 84.4 ± 28.5 nmol/min per mg mitochondrial protein). The ratio of complex I + III to citrate synthase decreased to 3.5 to 22.9% (normal control 66.1 ± 14.7%). The activities of complex III decreased to 10.4 to 49.3% of the lowest control value, while complex I, II, IV and V activities were normal. The results supported the diagnosis of isolated respiratory chain complex III deficiency.
  
  
  CONCLUSIONS
  Complex III deficiency is a kind of disorder of energy metabolism with various manifestations. The complex I + III activities and the ratio of complex I + III to citrate synthase were lower than those of the control. The activities of complex I, II, IV and V were normal.
authors.affiliation: Department of Pediatrics, Peking University First Hospital, Beijing, China.
authors.forename: Yan-yan
authors.initials: YY
authors.lastname: Ma
authors.forename: Tong-fei
authors.initials: TF
authors.lastname: Wu
authors.forename: Yu-peng
authors.initials: YP
authors.lastname: Liu
authors.forename: Qiao
authors.initials: Q
authors.lastname: Wang
authors.forename: Jin-qing
authors.initials: JQ
authors.lastname: Song
authors.forename: Jiang-xi
authors.initials: JX
authors.lastname: Xiao
authors.forename: Yu-wu
authors.initials: YW
authors.lastname: Jiang
authors.forename: Yan-ling
authors.initials: YL
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D042967:Electron Transport Complex I / Q000378:metabolism; D042963:Electron Transport Complex II / Q000378:metabolism; D014450:Electron Transport Complex III / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D007888:Leigh Disease; D007963:Leukocytes, Mononuclear / Q000201:enzymology*; D008297:Male; D028361:Mitochondrial Diseases / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D042963:Electron Transport Complex II; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III