Porfobilinogeno deaminasi

La porfobilinogeno deaminasi è un enzima (o meglio, sono due isoenzimi in base allo splicing alternativo) che trasforma il porfobilinogeno in idrossimetilbilano.

Porfobilinogeno deaminasi
Struttura quaternaria dell'enzima
Gene
HUGO	HMBS
Locus	Chr. 11 p23
Proteina
UniProt	P08397
Enzima
Numero EC	2.5.1.61

In particolare, questo enzima forma per deaminazione un legame tioetere con un residuo di porfobilinogeno, poi prosegue la deaminazione su altri cinque residui di porfobilinogeno così da formare una struttura esapirrolica. L'esapirrolo è scisso per idrolisi, in questo modo da una parte si ha il complesso porfobilinogeno deaminasi + dipirrometano, e dall'altra parte si libera idrossimetilbilano. L'enzima poi ricomincia il ciclo su altre molecole di porfobilinogeno.

L'idrossimetilbilano è una molecola instabile che si chiude spontaneamente in una struttura tetrapirrolica, formando l'uroporfirinogeno I. In base all'ordine in senso orario dei sostituenti dell'anello tetrapirrolico, l'uroporfirinogeno può rimanere tale o essere convertito dall'uroporfirinogeno III cosintasi in uroporfirinogeno III (ABABABAB si ottiene il tipo I, con ABABABBA si ottiene il tipo III).

Bibliografia

• Deybach JC, Puy H, Porphobilinogen deaminase gene structure and molecular defects., in J. Bioenerg. Biomembr., vol. 27, n. 2, 1995, pp. 197–205, DOI:10.1007/BF02110034, PMID 7592566.
• Astrin KH, Desnick RJ, Molecular basis of acute intermittent porphyria: mutations and polymorphisms in the human hydroxymethylbilane synthase gene., in Hum. Mutat., vol. 4, n. 4, 1995, pp. 243–52, DOI:10.1002/humu.1380040403, PMID 7866402.
• Helliwell JR, Nieh YP, Habash J, et al., Time-resolved and static-ensemble structural chemistry of hydroxymethylbilane synthase., in Faraday Discuss., vol. 122, 2003, pp. 131–44; discussion 171–90, DOI:10.1039/b201331b, PMID 12555854.
• Hessels J, Voortman G, van der Wagen A, et al., Homozygous acute intermittent porphyria in a 7-year-old boy with massive excretions of porphyrins and porphyrin precursors., in J. Inherit. Metab. Dis., vol. 27, n. 1, 2004, pp. 19–27, DOI:10.1023/B:BOLI.0000016613.75677.05, PMID 14970743.
• Kauppinen R, Molecular diagnostics of acute intermittent porphyria., in Expert Rev. Mol. Diagn., vol. 4, n. 2, 2004, pp. 243–9, DOI:10.1586/14737159.4.2.243, PMID 14995910.
• Hrdinka M, Puy H, Martasek P, May 2006 update in porphobilinogen deaminase gene polymorphisms and mutations causing acute intermittent porphyria: comparison with the situation in Slavic population., in Physiological research / Academia Scientiarum Bohemoslovaca, 55 Suppl 2, 2007, pp. S119–36, PMID 17298216.
• Kauppinen R, Peltonen L, Pihlaja H, Mustajoki P, CRIM-positive mutations of acute intermittent porphyria in Finland., in Hum. Mutat., vol. 1, n. 5, 1993, pp. 392–6, DOI:10.1002/humu.1380010508, PMID 1301948.
• Mgone CS, Lanyon WG, Moore MR, Connor JM, Detection of seven point mutations in the porphobilinogen deaminase gene in patients with acute intermittent porphyria, by direct sequencing of in vitro amplified cDNA., in Hum. Genet., vol. 90, 1–2, 1992, pp. 12–6, DOI:10.1007/BF00210738, PMID 1427766.
• Gu XF, de Rooij F, Voortman G, et al., High frequency of mutations in exon 10 of the porphobilinogen deaminase gene in patients with a CRIM-positive subtype of acute intermittent porphyria, in Am. J. Hum. Genet., vol. 51, n. 3, 1992, pp. 660–5, PMC 1682727, PMID 1496994.
• Delfau MH, Picat C, De Rooij F, et al., Molecular heterogeneity of acute intermittent porphyria: identification of four additional mutations resulting in the CRIM-negative subtype of the disease, in Am. J. Hum. Genet., vol. 49, n. 2, 1991, pp. 421–8, PMC 1683312, PMID 1714233.
• Namba H, Narahara K, Tsuji K, et al., Assignment of human porphobilinogen deaminase to 11q24.1----q24.2 by in situ hybridization and gene dosage studies, in Cytogenet. Cell Genet., vol. 57, 2–3, 1991, pp. 105–8, DOI:10.1159/000133123, PMID 1914516.
• Lee JS, Anvret M, Identification of the most common mutation within the porphobilinogen deaminase gene in Swedish patients with acute intermittent porphyria, in Proc. Natl. Acad. Sci. U.S.A., vol. 88, n. 23, 1992, pp. 10912–5, DOI:10.1073/pnas.88.23.10912, PMC 53042, PMID 1961762.
• Tunnacliffe A, McGuire RS, A physical linkage group in human chromosome band 11q23 covering a region implicated in leukocyte neoplasia, in Genomics, vol. 8, n. 3, 1991, pp. 447–53, DOI:10.1016/0888-7543(90)90030-X, PMID 1981047.
• Lander M, Pitt AR, Alefounder PR, et al., Studies on the mechanism of hydroxymethylbilane synthase concerning the role of arginine residues in substrate binding, in Biochem. J., vol. 275, n. 2, 1991, pp. 447–52, PMC 1150073, PMID 2025226.
• Scobie GA, Llewellyn DH, Urquhart AJ, et al., Acute intermittent porphyria caused by a C----T mutation that produces a stop codon in the porphobilinogen deaminase gene, in Hum. Genet., vol. 85, n. 6, 1990, pp. 631–4, DOI:10.1007/BF00193588, PMID 2227955.
• Delfau MH, Picat C, de Rooij FW, et al., Two different point G to A mutations in exon 10 of the porphobilinogen deaminase gene are responsible for acute intermittent porphyria, in J. Clin. Invest., vol. 86, n. 5, 1990, pp. 1511–6, DOI:10.1172/JCI114869, PMC 296897, PMID 2243128.
• Lannfelt L, Wetterberg L, Lilius L, et al., Porphobilinogen deaminase in human erythrocytes: purification of two forms with apparent molecular weights of 40 kDa and 42 kDa, in Scand. J. Clin. Lab. Invest., vol. 49, n. 7, 1990, pp. 677–84, DOI:10.3109/00365518909091544, PMID 2609111.
• Grandchamp B, Picat C, de Rooij F, et al., A point mutation G----A in exon 12 of the porphobilinogen deaminase gene results in exon skipping and is responsible for acute intermittent porphyria, in Nucleic Acids Res., vol. 17, n. 16, 1989, pp. 6637–49, DOI:10.1093/nar/17.16.6637, PMC 318356, PMID 2789372.
• Raich N, Romeo PH, Dubart A, et al., Molecular cloning and complete primary sequence of human erythrocyte porphobilinogen deaminase, in Nucleic Acids Res., vol. 14, n. 15, 1986, pp. 5955–68, DOI:10.1093/nar/14.15.5955, PMC 311614, PMID 2875434.
• Vidaud M, Gattoni R, Stevenin J, et al., A 5' splice-region G----C mutation in exon 1 of the human beta-globin gene inhibits pre-mRNA splicing: a mechanism for beta+-thalassemia, in Proc. Natl. Acad. Sci. U.S.A., vol. 86, n. 3, 1989, pp. 1041–5, DOI:10.1073/pnas.86.3.1041, PMC 286617, PMID 2915972.

Voci correlate

• Pirrolo