| Structural highlights
Disease
CBS_HUMAN Defects in CBS are the cause of cystathionine beta-synthase deficiency (CBSD) [MIM:236200. CBSD is an enzymatic deficiency resulting in altered sulfur metabolism and homocystinuria. The clinical features of untreated homocystinuria due to CBS deficiency include myopia, ectopia lentis, mental retardation, skeletal anomalies resembling Marfan syndrome, and thromboembolic events. Light skin and hair can also be present. Biochemical features include increased urinary homocystine and methionine.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35]
Function
CBS_HUMAN Only known pyridoxal phosphate-dependent enzyme that contains heme. Important regulator of hydrogen sulfide, especially in the brain, utilizing cysteine instead of serine to catalyze the formation of hydrogen sulfide. Hydrogen sulfide is a gastratransmitter with signaling and cytoprotective effects such as acting as a neuromodulator in the brain to protect neurons against hypoxic injury (By similarity).
Publication Abstract from PubMed
Cystathionine beta-synthase (CBS) is a pyridoxal-phosphate (PLP)-dependent enzyme essential for the reverse transsulfuration pathway, where homocysteine and serine combine to form cystathionine, the immediate precursor of cysteine. Mutations in the CBS gene cause homocystinuria, a disorder associated with intellectual disability, multisystem complications, and reduced life expectancy. The CBS p.R336C mutation, linked to severe pyridoxine non-responsiveness, results in reduced enzyme activity, previously attributed to protein instability and weakened substrate and PLP binding. To clarify the effects of the pathological R336C mutation, we performed biochemical, biophysical, and crystallographic analyses, as well as molecular dynamics simulations. Our findings show that the R336C mutation minimally impacts the structural environment around residue 336, does not cause enzyme misfolding, and does not impair the binding of PLP or the allosteric activator S-adenosylmethionine (AdoMet) binding. Instead, the mutation induces subtle reorientations in nearby hydrophobic residues, including F185 and Y381, altering intramolecular contacts that perturb the interaction between asparagine 149 and the O3 oxygen of PLP. This alteration is known to potentially shift the tautomeric equilibrium of the PLP Schiff base from its catalytically active ketoenamine form to the inactive enolimine form, which aligns with the reduced activity of the R336C variant. Additionally, the R336C mutation disrupts intermolecular contacts between the catalytic core and Bateman module, altering the Bateman module's intrinsic mobility in the enzyme's basal state and potentially affecting the cavity opening required for catalysis. Importantly, the R336C variant retains the native enzyme's ability to assemble into polymeric chains in crystals, preserving its filament formation capacity.
The disease-linked R336C mutation in cystathionine beta-synthase disrupts communication with the PLP cofactor, yet maintains the enzyme's overall structural integrity.,Conter C, Nunez-Franco R, Al-Sadeq DW, Fernandez-Rodriguez C, Goikoetxea-Usandizaga N, Nasrallah GK, Nomikos M, Martinez-Chantar ML, Astegno A, Jimenez-Oses G, Martinez-Cruz LA FEBS J. 2025 May 6. doi: 10.1111/febs.70116. PMID:40327797[36]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Kozich V, Kraus JP. Screening for mutations by expressing patient cDNA segments in E. coli: homocystinuria due to cystathionine beta-synthase deficiency. Hum Mutat. 1992;1(2):113-23. PMID:1301198 doi:http://dx.doi.org/10.1002/humu.1380010206
- ↑ Kozich V, de Franchis R, Kraus JP. Molecular defect in a patient with pyridoxine-responsive homocystinuria. Hum Mol Genet. 1993 Jun;2(6):815-6. PMID:8353501
- ↑ Hu FL, Gu Z, Kozich V, Kraus JP, Ramesh V, Shih VE. Molecular basis of cystathionine beta-synthase deficiency in pyridoxine responsive and nonresponsive homocystinuria. Hum Mol Genet. 1993 Nov;2(11):1857-60. PMID:7506602
- ↑ de Franchis R, Kozich V, McInnes RR, Kraus JP. Identical genotypes in siblings with different homocystinuric phenotypes: identification of three mutations in cystathionine beta-synthase using an improved bacterial expression system. Hum Mol Genet. 1994 Jul;3(7):1103-8. PMID:7981678
- ↑ Marble M, Geraghty MT, de Franchis R, Kraus JP, Valle D. Characterization of a cystathionine beta-synthase allele with three mutations in cis in a patient with B6 nonresponsive homocystinuria. Hum Mol Genet. 1994 Oct;3(10):1883-6. PMID:7849717
- ↑ Kraus JP. Komrower Lecture. Molecular basis of phenotype expression in homocystinuria. J Inherit Metab Dis. 1994;17(4):383-90. PMID:7967489
- ↑ Shih VE, Fringer JM, Mandell R, Kraus JP, Berry GT, Heidenreich RA, Korson MS, Levy HL, Ramesh V. A missense mutation (I278T) in the cystathionine beta-synthase gene prevalent in pyridoxine-responsive homocystinuria and associated with mild clinical phenotype. Am J Hum Genet. 1995 Jul;57(1):34-9. PMID:7611293
- ↑ Sebastio G, Sperandeo MP, Panico M, de Franchis R, Kraus JP, Andria G. The molecular basis of homocystinuria due to cystathionine beta-synthase deficiency in Italian families, and report of four novel mutations. Am J Hum Genet. 1995 Jun;56(6):1324-33. PMID:7762555
- ↑ Kluijtmans LA, Blom HJ, Boers GH, van Oost BA, Trijbels FJ, van den Heuvel LP. Two novel missense mutations in the cystathionine beta-synthase gene in homocystinuric patients. Hum Genet. 1995 Aug;96(2):249-50. PMID:7635485
- ↑ Kruger WD, Cox DR. A yeast assay for functional detection of mutations in the human cystathionine beta-synthase gene. Hum Mol Genet. 1995 Jul;4(7):1155-61. PMID:8528202
- ↑ Sperandeo MP, Panico M, Pepe A, Candito M, de Franchis R, Kraus JP, Andria G, Sebastio G. Molecular analysis of patients affected by homocystinuria due to cystathionine beta-synthase deficiency: report of a new mutation in exon 8 and a deletion in intron 11. J Inherit Metab Dis. 1995;18(2):211-4. PMID:7564249
- ↑ Kluijtmans LA, Boers GH, Stevens EM, Renier WO, Kraus JP, Trijbels FJ, van den Heuvel LP, Blom HJ. Defective cystathionine beta-synthase regulation by S-adenosylmethionine in a partially pyridoxine responsive homocystinuria patient. J Clin Invest. 1996 Jul 15;98(2):285-9. PMID:8755636 doi:10.1172/JCI118791
- ↑ Sperandeo MP, Candito M, Sebastio G, Rolland MO, Turc-Carel C, Giudicelli H, Dellamonica P, Andria G. Homocysteine response to methionine challenge in four obligate heterozygotes for homocystinuria and relationship with cystathionine beta-synthase mutations. J Inherit Metab Dis. 1996;19(3):351-6. PMID:8803779
- ↑ Dawson PA, Cox AJ, Emmerson BT, Dudman NP, Kraus JP, Gordon RB. Characterisation of five missense mutations in the cystathionine beta-synthase gene from three patients with B6-nonresponsive homocystinuria. Eur J Hum Genet. 1997 Jan-Feb;5(1):15-21. PMID:9156316
- ↑ Kim CE, Gallagher PM, Guttormsen AB, Refsum H, Ueland PM, Ose L, Folling I, Whitehead AS, Tsai MY, Kruger WD. Functional modeling of vitamin responsiveness in yeast: a common pyridoxine-responsive cystathionine beta-synthase mutation in homocystinuria. Hum Mol Genet. 1997 Dec;6(13):2213-21. PMID:9361025
- ↑ Aral B, Coude M, London J, Aupetit J, Chasse JF, Zabot MT, Chadefaux-Vekemans B, Kamoun P. Two novel mutations (K384E and L539S) in the C-terminal moiety of the cystathionine beta-synthase protein in two French pyridoxine-responsive homocystinuria patients. Hum Mutat. 1997;9(1):81-2. PMID:8990018 doi:<81::AID-HUMU18>3.0.CO;2-L 10.1002/(SICI)1098-1004(1997)9:1<81::AID-HUMU18>3.0.CO;2-L
- ↑ Kozich V, Janosik M, Sokolova J, Oliveriusova J, Orendac M, Kraus JP, Elleder D. Analysis of CBS alleles in Czech and Slovak patients with homocystinuria: report on three novel mutations E176K, W409X and 1223 + 37 del99. J Inherit Metab Dis. 1997 Jul;20(3):363-6. PMID:9266356
- ↑ Tsai MY, Wong PW, Garg U, Hanson NQ, Schwichtenberg K. Two Novel Mutations in the Cystathionine beta-synthase Gene of Homocystinuric Patients. Mol Diagn. 1997 Jun;2(2):129-133. PMID:10462600 doi:10.1054/MODI00200129
- ↑ Gordon RB, Cox AJ, Dawson PA, Emmerson BT, Kraus JP, Dudman NP. Mutational analysis of the cystathionine beta-synthase gene: a splicing mutation, two missense mutations and an insertion in patients with homocystinuria. Mutations in brief no. 120. Online. Hum Mutat. 1998;11(4):332. PMID:10215408 doi:<332::AID-HUMU16>3.0.CO;2-P 10.1002/(SICI)1098-1004(1998)11:4<332::AID-HUMU16>3.0.CO;2-P
- ↑ Gallagher PM, Naughten E, Hanson NQ, Schwichtenberg K, Bignell M, Yuan M, Ward P, Yap S, Whitehead AS, Tsai MY. Characterization of mutations in the cystathionine beta-synthase gene in Irish patients with homocystinuria. Mol Genet Metab. 1998 Dec;65(4):298-302. PMID:9889017 doi:10.1006/mgme.1998.2771
- ↑ de Franchis R, Kraus E, Kozich V, Sebastio G, Kraus JP. Four novel mutations in the cystathionine beta-synthase gene: effect of a second linked mutation on the severity of the homocystinuric phenotype. Hum Mutat. 1999;13(6):453-7. PMID:10408774 doi:<453::AID-HUMU4>3.0.CO;2-K 10.1002/(SICI)1098-1004(1999)13:6<453::AID-HUMU4>3.0.CO;2-K
- ↑ Gat-Yablonski G, Mandel H, Fowler B, Taleb O, Sela BA. Homocystinuria in the Arab population of Israel: identification of two novel mutations using DGGE analysis. Hum Mutat. 2000 Oct;16(4):372. PMID:11013450 doi:<372::AID-HUMU12>3.0.CO;2-J 10.1002/1098-1004(200010)16:4<372::AID-HUMU12>3.0.CO;2-J
- ↑ Janosik M, Oliveriusova J, Janosikova B, Sokolova J, Kraus E, Kraus JP, Kozich V. Impaired heme binding and aggregation of mutant cystathionine beta-synthase subunits in homocystinuria. Am J Hum Genet. 2001 Jun;68(6):1506-13. Epub 2001 May 15. PMID:11359213 doi:10.1086/320597
- ↑ Castro R, Heil SG, Rivera I, Jakobs C, de Almeida IT, Blom HJ. Molecular genetic analysis of the cystathionine beta-synthase gene in Portuguese homocystinuria patients: three novel mutations. Clin Genet. 2001 Aug;60(2):161-3. PMID:11553052
- ↑ Maclean KN, Gaustadnes M, Oliveriusova J, Janosik M, Kraus E, Kozich V, Kery V, Skovby F, Rudiger N, Ingerslev J, Stabler SP, Allen RH, Kraus JP. High homocysteine and thrombosis without connective tissue disorders are associated with a novel class of cystathionine beta-synthase (CBS) mutations. Hum Mutat. 2002 Jun;19(6):641-55. PMID:12007221 doi:10.1002/humu.10089
- ↑ Gaustadnes M, Wilcken B, Oliveriusova J, McGill J, Fletcher J, Kraus JP, Wilcken DE. The molecular basis of cystathionine beta-synthase deficiency in Australian patients: genotype-phenotype correlations and response to treatment. Hum Mutat. 2002 Aug;20(2):117-26. PMID:12124992 doi:10.1002/humu.10104
- ↑ Urreizti R, Balcells S, Rodes M, Vilarinho L, Baldellou A, Couce ML, Munoz C, Campistol J, Pinto X, Vilaseca MA, Grinberg D. Spectrum of CBS mutations in 16 homocystinuric patients from the Iberian Peninsula: high prevalence of T191M and absence of I278T or G307S. Hum Mutat. 2003 Jul;22(1):103. PMID:12815602 doi:10.1002/humu.9153
- ↑ Kruger WD, Wang L, Jhee KH, Singh RH, Elsas LJ 2nd. Cystathionine beta-synthase deficiency in Georgia (USA): correlation of clinical and biochemical phenotype with genotype. Hum Mutat. 2003 Dec;22(6):434-41. PMID:14635102 doi:10.1002/humu.10290
- ↑ Orendae M, Pronicka E, Kubalska J, Janosik M, Sokolova J, Linnebank M, Koch HG, Kozich V. Identification and functional analysis of two novel mutations in the CBS gene in Polish patients with homocystinuria. Hum Mutat. 2004 Jun;23(6):631. PMID:15146473 doi:10.1002/humu.9249
- ↑ Linnebank M, Janosik M, Kozich V, Pronicka E, Kubalska J, Sokolova J, Linnebank A, Schmidt E, Leyendecker C, Klockgether T, Kraus JP, Koch HG. The cystathionine beta-synthase (CBS) mutation c.1224-2A>C in Central Europe: Vitamin B6 nonresponsiveness and a common ancestral haplotype. Hum Mutat. 2004 Oct;24(4):352-3. PMID:15365998 doi:10.1002/humu.9280
- ↑ Porto MP, Galdieri LC, Pereira VG, Vergani N, da Rocha JC, Micheletti C, Martins AM, Perez AB, Almeida VD. Molecular analysis of homocystinuria in Brazilian patients. Clin Chim Acta. 2005 Dec;362(1-2):71-8. Epub 2005 Jul 5. PMID:15993874 doi:10.1016/j.cccn.2005.05.030
- ↑ Lee SJ, Lee DH, Yoo HW, Koo SK, Park ES, Park JW, Lim HG, Jung SC. Identification and functional analysis of cystathionine beta-synthase gene mutations in patients with homocystinuria. J Hum Genet. 2005;50(12):648-54. Epub 2005 Oct 5. PMID:16205833 doi:10.1007/s10038-005-0312-2
- ↑ Urreizti R, Asteggiano C, Cozar M, Frank N, Vilaseca MA, Grinberg D, Balcells S. Functional assays testing pathogenicity of 14 cystathionine-beta synthase mutations. Hum Mutat. 2006 Feb;27(2):211. PMID:16429402 doi:10.1002/humu.9395
- ↑ Cozar M, Urreizti R, Vilarinho L, Grosso C, Dodelson de Kremer R, Asteggiano CG, Dalmau J, Garcia AM, Vilaseca MA, Grinberg D, Balcells S. Identification and functional analyses of CBS alleles in Spanish and Argentinian homocystinuric patients. Hum Mutat. 2011 Jul;32(7):835-42. doi: 10.1002/humu.21514. Epub 2011 Jun 7. PMID:21520339 doi:10.1002/humu.21514
- ↑ Kwok JS, Fung SL, Lui GC, Law EL, Chan MH, Leung CB, Tang NL. CBS gene mutations found in a Chinese pyridoxine-responsive homocystinuria patient. Pathology. 2011 Jan;43(1):81-3. doi: 10.1097/PAT.0b013e3283419dbb. PMID:21240075 doi:10.1097/PAT.0b013e3283419dbb
- ↑ Conter C, Núñez-Franco R, Al-Sadeq DW, Fernández-Rodríguez C, Goikoetxea-Usandizaga N, Nasrallah GK, Nomikos M, Martinez-Chantar ML, Astegno A, Jiménez-Osés G, Martínez-Cruz LA. The disease-linked R336C mutation in cystathionine β-synthase disrupts communication with the PLP cofactor, yet maintains the enzyme's overall structural integrity. FEBS J. 2025 May 6. PMID:40327797 doi:10.1111/febs.70116
|
