>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=92.34  E-value=0.57  Score=25.70  Aligned_cols=132  Identities=20%  Similarity=0.223  Sum_probs=75.2

Q ss_pred             HHHHHHHCCCCCCCH-HC----CCC-HHHHHHHCCCCCCCCCCCCCCCCCCC------CCCCCCCCCCCCCEEEECCCHH
Q ss_conf             988643103221100-00----367-56754200233322222222211122------2211111233432023101012
Q gi|254781112|r   93 GLITGLDTNRYDVLV-NV----AIT-PERQKKYDFSIPYIAHRVLLVVRSDQ------QDIRSFKDLTDKTVAQILGTDL  160 (274)
Q Consensus        93 ~~~~~l~~g~~D~~~-~~----~~t-~eR~~~~~fs~p~~~~~~~~~~~~~~------~~~~~~~dL~g~~V~~~~g~~~  160 (274)
T Consensus        62 Ele~aLL~geiD~AVHSlKD~P~~~~~~g---L--------~~~a~~~RedP~D~l~s~~~~~l~~LP---~GA~vGTSS  127 (312)
T TIGR00212        62 ELEQALLDGEIDLAVHSLKDVPTVLSPEG---L--------EIAAVLKREDPRDVLVSRKYLSLEELP---QGAKVGTSS  127 (312)
T ss_pred             HHHHHHHCCCCCEEEECCCCCCCCCCCCC---C--------EEEEECCCCCCCCEEEECCCCCHHHCC---CCCEEECCH
T ss_conf             99999625984488843023576559888---2--------786355878864268862788851277---988897457


Q ss_pred             HH---HHHC--CCCCCEEEC-CHHHHHHHHHH-HHHHCCCCCHHHHHHHHHHCCCCC-CCEE-----ECCCCCCCCCEEE
Q ss_conf             23---3201--345421336-85577775544-321003665589999998458766-7326-----2367768770799
Q gi|254781112|r  161 SR---FAKE--LKSHLVFSH-NFEQSLQLLLS-KRTDATMIPDIPFFNFLERRPHDG-NLFK-----IADRMKDNSAVAF  227 (274)
Q Consensus       161 ~~---~l~~--~~~~~~~~~-~~~~~~~~l~~-grvD~~~~~~~~~~~~~~~~~~~~-~~~~-----~~~~~~~~~~~~~  227 (274)
T Consensus       128 ~RR~aql~~~RPDl~~~~lRGNi~TRl~Kl~~Gg~~DAiiLA~A----GL~RLg~~~~~i~~~~~~~~~~PA~GQG~i~v  203 (312)
T TIGR00212       128 LRRKAQLKALRPDLEIEPLRGNIDTRLRKLDEGGEYDAIILAAA----GLKRLGLENDVITEVLDPEVMLPAVGQGAIAV  203 (312)
T ss_pred             HHHHHHHHHCCCCCEEEECCCCHHHHHHHHCCCCCCHHHHHHHH----HHHCCCCCCHHHHHCCCHHHCCCCCCCCEEEE
T ss_conf             99999998308994499746987999998518882048999888----75302541013431478114178866757999


Q ss_pred             EEECCCHHHHHHHHH
Q ss_conf             981899899999999
Q gi|254781112|r  228 MMRKGNNKLTRSINE  242 (274)
Q Consensus       228 ~~~k~~~~L~~~in~  242 (274)
T Consensus       204 e~R~dD~~~~~il~~  218 (312)
T TIGR00212       204 ECRKDDTEIKEILKE  218 (312)
T ss_pred             EEECCCHHHHHHHHH
T ss_conf             984587799998620