Cystathionine c-lyase: Clinical, metabolic, genetic, and structural studies Jan P. Kraus a , Jindr ˇich Hašek b , Viktor Koz ˇich c , Renata Collard a , Sarah Venezia a , Bohumila Janošíková c , Jian Wang d , Sally P. Stabler e , Robert H. Allen e , Cornelis Jakobs f , Christine T. Finn g , Yin-Hsiu Chien h , Wuh-Liang Hwu h , Robert A. Hegele d , S. Harvey Mudd i, * a Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO, USA b Department of Structure Analysis, Institute of Macromolecular Chemistry AS CR, Prague, Czech Republic c Institute of Inherited Metabolic Diseases, Charles University in Prague-First Faculty of Medicine, Prague, Czech Republic d Robarts Research Institute, London, Ont., Canada e Division of Hematology, University of Colorado Health Sciences Center, Aurora, CO, USA f Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands g Massachusetts General Hospital, Department of Psychiatry, Harvard-Partners Center for Genetics and Genomics, Boston, MA, USA h Departments of Medical Genetics and Pediatrics, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan i Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD, USA article info Article history: Received 23 January 2009 Received in revised form 1 April 2009 Accepted 2 April 2009 Available online xxxx Keywords: Cystathionine c-lyase Cystathioninuria Hypercystathioninemia Mutations Deletion abstract We report studies of six individuals with marked elevations of cystathionine in plasma and/or urine. Studies of CTH, the gene that encodes cystathionine c-lyase, revealed the presence among these individ- uals of either homozygous or compound heterozygous forms of a novel large deletion, p.Gly57_Gln196- del, two novel missense mutations, c.589C>T (p.Arg197Cys) and c.932C>T (p.Thr311Ile), and one previously reported alteration, c.200C>T (p.Thr67Ile). Another novel missense mutation, c.185G>T (p.Arg62His), was found in heterozygous form in three mildly hypercystathioninemic members of a Tai- wanese family. In one severely hypercystathioninemic individual no CTH mutation was found. Brief clin- ical histories of the cystathioninemic/cystathioninuric patients are presented. Most of the novel mutations were expressed and the CTH activities of the mutant proteins determined. The crystal struc- ture of the human enzyme, hCTH, and the evidence available as to the effects of the mutations in ques- tion, as well as those of the previously reported p.Gln240Glu, on protein structure, enzymatic activity, and responsiveness to vitamin B 6 administration are discussed. Among healthy Czech controls, 9.3% were homozygous for CTH c.1208G>T (p.Ser403Ile), previously found homozygously in 7.5% of Canadians for whom plasma total homocysteine (tHcy) had been measured. Compared to wild-type homozygotes, among the 55 Czech c.1208G>T (p.Ser403Ile) homozygotes a greater level of plasma cystathionine was found only after methionine loading. Three of the four individuals homozygous or compound heterozy- gous for inactivating CTH mutations had mild plasma tHcy elevations, perhaps indicating a cause-and- effect relationship. The experience with the present patients provides no evidence that severe loss of CTH activity is accompanied by adverse clinical effects. Published by Elsevier Inc. Introduction Cystathioninuria or hypercystathioninemia may be due to a variety of causes. Less marked elevations of urinary excretion and/or plasma concentrations occur with prematurity, deficiencies of vitamins B 6 ,B 12 , or folic acid, neural tumors that produce cysta- thionine, a renal defect in the transport of this amino acid, or in genetically determined defects in the conversion of homocysteine to methionine. In the latter situation the excessive accumulation of homocysteine leads to an abnormally high rate of production of cystathionine by cystathionine b-synthase. These conditions have been reviewed in more detail elsewhere [1,2]. More marked cystathioninuria and hypercystathioninemia of genetic origin is caused by mutations that decrease the activity of cystathionine c- lyase (CTH; EC 4.4.1.1) 1 , the enzyme that catalyzes the conversion of cystathionine to cysteine, ammonia, and 2-oxobutyrate. The initial patient in whom the metabolic findings strongly suggested a CTH de- fect was reported in 1959 by Harris and colleagues [3], and by 1983 a survey of published cases listed briefly the metabolic and clinical findings in a total of 47 such cases with gross cystathioninuria thought to be of genetic origin [4]. However, among these cases the 1096-7192/$ - see front matter Published by Elsevier Inc. doi:10.1016/j.ymgme.2009.04.001 * Corresponding author. Fax: +1 301 402 0245. E-mail address: muddh@mail.nih.gov (S.H. Mudd). 1 The name for the same enzyme has also been abbreviated as ‘‘Cse”, ‘‘CGL”, and ‘‘CTT”. Molecular Genetics and Metabolism xxx (2009) xxx–xxx Contents lists available at ScienceDirect Molecular Genetics and Metabolism journal homepage: www.elsevier.com/locate/ymgme ARTICLE IN PRESS Please cite this article in press as: J.P. Kraus et al., Cystathionine c-lyase: Clinical, metabolic, genetic, and structural studies, Mol. Genet. Metab. (2009), doi:10.1016/j.ymgme.2009.04.001