>TIGR00212 hemC porphobilinogen deaminase; InterPro: IPR000860 Tetrapyrroles are large macrocyclic compounds derived from a common biosynthetic pathway . The end-product, uroporphyrinogen III, is used to synthesise a number of important molecules, including vitamin B12, haem, sirohaem, chlorophyll, coenzyme F430 and phytochromobilin . The first stage in tetrapyrrole synthesis is the synthesis of 5-aminoaevulinic acid ALA via two possible routes: (1) condensation of succinyl CoA and glycine (C4 pathway) using ALA synthase (2.3.1.37 from EC), or (2) decarboxylation of glutamate (C5 pathway) via three different enzymes, glutamyl-tRNA synthetase (6.1.1.17 from EC) to charge a tRNA with glutamate, glutamyl-tRNA reductase (1.2.1.70 from EC) to reduce glutamyl-tRNA to glutamate-1-semialdehyde (GSA), and GSA aminotransferase (5.4.3.8 from EC) to catalyse a transamination reaction to produce ALA. The second stage is to convert ALA to uroporphyrinogen III, the first macrocyclic tetrapyrrolic structure in the pathway. This is achieved by the action of three enzymes in one common pathway: porphobilinogen (PBG) synthase (or ALA dehydratase, 4.2.1.24 from EC) to condense two ALA molecules to generate porphobilinogen; hydroxymethylbilane synthase (or PBG deaminase, 2.5.1.61 from EC) to polymerise four PBG molecules into preuroporphyrinogen (tetrapyrrole structure); and uroporphyrinogen III synthase (4.2.1.75 from EC) to link two pyrrole units together (rings A and D) to yield uroporphyrinogen III. Uroporphyrinogen III is the first branch point of the pathway. To synthesise cobalamin (vitamin B12), sirohaem, and coenzyme F430, uroporphyrinogen III needs to be converted into precorrin-2 by the action of uroporphyrinogen III methyltransferase (2.1.1.107 from EC). To synthesise haem and chlorophyll, uroporphyrinogen III needs to be decarboxylated into coproporphyrinogen III by the action of uroporphyrinogen III decarboxylase (4.1.1.37 from EC) . This entry represents hydroxymethylbilane synthase (or porphobilinogen deaminase, 2.5.1.61 from EC), which functions during the second stage of tetrapyrrole biosynthesis. This enzyme catalyses the polymerisation of four PBG molecules into the tetrapyrrole structure, preuroporphyrinogen, with the concomitant release of four molecules of ammonia. This enzyme uses a unique dipyrro-methane cofactor made from two molecules of PBG, which is covalently attached to a cysteine side chain. The tetrapyrrole product is synthesized in an ordered, sequential fashion, by initial attachment of the first pyrrole unit (ring A) to the cofactor, followed by subsequent additions of the remaining pyrrole units (rings B, C, D) to the growing pyrrole chain . The link between the pyrrole ring and the cofactor is broken once all the pyrroles have been added. This enzyme is folded into three distinct domains that enclose a single, large active site that makes use of an aspartic acid as its one essential catalytic residue, acting as a general acid/base during catalysis , . A deficiency of hydroxymethylbilane synthase is implicated in the neuropathic disease, Acute Intermittent Porphyria (AIP) . ; GO: 0004418 hydroxymethylbilane synthase activity, 0033014 tetrapyrrole biosynthetic process.

Probab=95.98  E-value=0.043  Score=33.54  Aligned_cols=136  Identities=18%  Similarity=0.164  Sum_probs=86.7

Q ss_pred             CCHHHHHCCCEEEEEECCCCCCCCHHCCCCCCCCCCC-CCCEE---EEEECC-------CCCCCHHHH-CCCCEEEEECC
Q ss_conf             0026774396279981243253201102784353223-44023---463021-------134753641-78620343134
Q gi|254780170|r   87 ERFLALQSKQIDILSRNTDWTLLREISLGLAFRPITY-FDGQG---FIMHKK-------KGISSVSQL-SGASICVQAGT  154 (342)
Q Consensus        87 ~rf~aL~sG~vDil~~~~T~T~~Rd~~~~v~Fs~~~~-~dgq~---~lVrk~-------~~i~s~~dL-~G~~I~v~~GT  154 (342)
T Consensus        62 Ele~aLL~geiD~AVHSl---------KD~---P~~~~~~gL~~~a~~~RedP~D~l~s~~~~~l~~LP~GA~vG----T  125 (312)
T TIGR00212        62 ELEQALLDGEIDLAVHSL---------KDV---PTVLSPEGLEIAAVLKREDPRDVLVSRKYLSLEELPQGAKVG----T  125 (312)
T ss_pred             HHHHHHHCCCCCEEEECC---------CCC---CCCCCCCCCEEEEECCCCCCCCEEEECCCCCHHHCCCCCEEE----C
T ss_conf             999996259844888430---------235---765598882786355878864268862788851277988897----4


Q ss_pred             CHHHHHHHHHHHCCCCCCEEEECCH-HHHHHHHHC-CCEEEEEECCHHHHH-HHHHCCCC-HHHCCCCCCCCCC----CE
Q ss_conf             2699999999862998507874798-999999873-960299825047999-99836780-0100256444237----10
Q gi|254780170|r  155 TTELTLADYFKAHNMKYHPIVFERV-EEIDAAYRA-HRCDAYTGDISALYA-LKLTNDRP-SEHVILPDIISKS----PL  226 (342)
Q Consensus       155 T~e~~l~~~~~~~~~~~~~v~~~~~-~~a~~al~~-Gr~DA~~~D~s~La~-~~~~~~~p-~~~~il~e~iskE----Pl  226 (342)
T Consensus       126 SS~RR-~aql~~~RPDl~~~~lRGNi~TRl~Kl~~Gg~~DAiiL---A~AGL~RLg~~~~~i~~~~~~~~~~PA~GQG~i  201 (312)
T TIGR00212       126 SSLRR-KAQLKALRPDLEIEPLRGNIDTRLRKLDEGGEYDAIIL---AAAGLKRLGLENDVITEVLDPEVMLPAVGQGAI  201 (312)
T ss_pred             CHHHH-HHHHHHCCCCCEEEECCCCHHHHHHHHCCCCCCHHHHH---HHHHHHCCCCCCHHHHHCCCHHHCCCCCCCCEE
T ss_conf             57999-99998308994499746987999998518882048999---888753025410134314781141788667579


Q ss_pred             EEECCCCCHHHHHHHH
Q ss_conf             1000277757999988
Q gi|254780170|r  227 APAIIQGDTEWYNIVS  242 (342)
Q Consensus       227 g~avr~gD~~w~d~V~  242 (342)
T Consensus       202 ~ve~R~dD~~~~~il~  217 (312)
T TIGR00212       202 AVECRKDDTEIKEILK  217 (312)
T ss_pred             EEEEECCCHHHHHHHH
T ss_conf             9998458779999862