ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, tryptophan hydroxylases (TPH), both peripheral (TPH1) and neuronal (TPH2) enzymes; ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, tryptophan hydroxylases (TPH), both peripheral (TPH1) and neuronal (TPH2) enzymes. TPH catalyses the hydroxylation of L-Trp to 5-hydroxytryptophan, the rate limiting step in the biosynthesis of 5-hydroxytryptamine (serotonin) and the first reaction in the synthesis of melatonin. Very little is known about the role of the ACT domain in TPH, which appears to be regulated by phosphorylation but not by its substrate or cofactor. Members of this CD belong to the superfamily of ACT regulatory domains.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 444909167  22 TLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISREQLNDIFPLLKSHATVLSVDS 94
Cdd:cd04929    2 SVIFSLKNEVGGLAKALKLFQELGINVVHIESRKSKRRSSEFEIFVDCECDQRRLDELVQLLKREVASVNMNT 74

Prephenate dehydratase [Amino acid transport and metabolism]; Prephenate dehydratase is part of the Pathway/BioSystem: Aromatic amino acid biosynthesis

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 444909167   2 IEDNKEN-------KENKDHSSERGRVTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISRE 74
Cdd:COG0077  166 IEDNPNNttrflvlGREPAAPTGADKTSLVFSLPNRPGALYKALGVFATRGINLTKIESRPIKGGLWEYVFFIDVEGHID 245

                 .
gi 444909167  75 Q 75
Cdd:COG0077  246 D 246

phenylalanine-4-hydroxylase, tetrameric form; This model describes the larger, tetrameric form of phenylalanine-4-hydroxylase, as found in metazoans. The enzyme irreversibly converts phenylalanine to tryosine and is known to be the rate-limiting step in phenylalanine catabolism in some systems. It is closely related to metazoan tyrosine 3-monooxygenase and tryptophan 5-monoxygenase, and more distantly to monomeric phenylalanine-4-hydroxylases of some Gram-negative bacteria. The member of this family from Drosophila has been described as having both phenylalanine-4-hydroxylase and tryptophan 5-monoxygenase activity (. However, a Drosophila member of the tryptophan 5-monoxygenase clade has subsequently been discovered.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 444909167   18 RGRVTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDI-SREQLNDIFPLLKSHATV----LSV 92
Cdd:TIGR01268  14 IAKTSLIFSLKEEAGALAETLKLFQAHDVNLTHIESRPSKTHPGEYEFFVEFDEaSDRKLEGVIEHLRQKAEVtvniLSR 93

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|....*
gi 444909167   93 DSPDQLTAkedvmetVPWFPKKISDLDFCANRVLLYGSELDADHP 137
Cdd:TIGR01268  94 DNKQNKDS-------VPWFPRKINDIDRFANQILSYGAELDADHP 131

ACT domain of the nonheme iron-dependent, aromatic amino acid hydroxylases (AAAH); ACT domain of the nonheme iron-dependent, aromatic amino acid hydroxylases (AAAH): Phenylalanine hydroxylases (PAH), tyrosine hydroxylases (TH) and tryptophan hydroxylases (TPH), both peripheral (TPH1) and neuronal (TPH2) enzymes. This family of enzymes shares a common catalytic mechanism, in which dioxygen is used by an active site containing a single, reduced iron atom to hydroxylate an unactivated aromatic substrate, concomitant with a two-electron oxidation of tetrahydropterin (BH4) cofactor to its quinonoid dihydropterin form. PAH catalyzes the hydroxylation of L-Phe to L-Tyr, the first step in the catabolic degradation of L-Phe; TH catalyses the hydroxylation of L-Tyr to 3,4-dihydroxyphenylalanine, the rate limiting step in the biosynthesis of catecholamines; and TPH catalyses the hydroxylation of L-Trp to 5-hydroxytryptophan, the rate limiting step in the biosynthesis of 5-hydroxytryptamine (serotonin) and the first reaction in the synthesis of melatonin. Eukaryotic AAAHs have an N-terminal ACT (regulatory) domain, a middle catalytic domain and a C-terminal domain which is responsible for the oligomeric state of the enzyme forming a domain-swapped tetrameric coiled-coil. The PAH, TH, and TPH enzymes contain highly conserved catalytic domains but distinct N-terminal ACT domains (this CD) and differ in their mechanisms of regulation. One commonality is that all three eukaryotic enzymes are regulated in part by the phosphorylation of serine residues N-terminal of the ACT domain. Members of this CD belong to the superfamily of ACT regulatory domains.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 444909167  21 VTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISREQLNDIFPLLKSHATVLSVDS 94
Cdd:cd04904    1 TSLIFSLKEEVGALARALKLFEEFGVNLTHIESRPSRRNGSEYEFFVDCEVDRGDLDQLISSLRRVVADVNILS 74

ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, phenylalanine hydroxylases (PAH); ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, phenylalanine hydroxylases (PAH). PAH catalyzes the hydroxylation of L-Phe to L-Tyr, the first step in the catabolic degradation of L-Phe. In PAH, an autoregulatory sequence, N-terminal of the ACT domain, extends across the catalytic domain active site and regulates the enzyme by intrasteric regulation. It appears that the activation by L-Phe induces a conformational change that converts the enzyme to a high-affinity and high-activity state. Modulation of activity is achieved through inhibition by BH4 and activation by phosphorylation of serine residues of the autoregulatory region. The molecular basis for the cooperative activation process is not fully understood yet. Members of this CD belong to the superfamily of ACT regulatory domains.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 444909167  12 KDHSSERGRVTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCD-ISREQLNDIFPLLKS 85
Cdd:cd04931    6 EENSNKNGVISLIFSLKEEVGALAKVLRLFEEKDINLTHIESRPSRLNKDEYEFFINLDkKSAPALDPIIKSLRN 80

Eukaryotic tryptophan hydroxylase (TrpOH); a member of the biopterin-dependent aromatic amino acid hydroxylase family of non-heme, iron(II)-dependent enzymes that also includes prokaryotic and eukaryotic phenylalanine-4-hydroxylase (PheOH) and eukaryotic tyrosine hydroxylase (TyrOH). TrpOH oxidizes L-tryptophan to 5-hydroxy-L-tryptophan, the rate-limiting step in the biosynthesis of serotonin (5-hydroxytryptamine), a widely distributed hormone and neurotransmitter.

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                 ....*....|....*....|....*....|....*....|
gi 444909167 109 PWFPKKISDLDFCANRVLLYGSELDADHP---VNMFTKSR 145
Cdd:cd03346    1 PWFPKKISDLDKCANRVLMYGSELDADHPgfkDNVYRKRR 40

Prephenate dehydratase [Amino acid transport and metabolism]; Prephenate dehydratase is part of the Pathway/BioSystem: Aromatic amino acid biosynthesis

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 444909167   2 IEDNKEN-------KENKDHSSERGRVTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISRE 74
Cdd:COG0077  166 IEDNPNNttrflvlGREPAAPTGADKTSLVFSLPNRPGALYKALGVFATRGINLTKIESRPIKGGLWEYVFFIDVEGHID 245

                 .
gi 444909167  75 Q 75
Cdd:COG0077  246 D 246

ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, tyrosine hydroxylases (TH); ACT domain of the nonheme iron-dependent aromatic amino acid hydroxylase, tyrosine hydroxylases (TH). TH catalyses the hydroxylation of L-Tyr to 3,4-dihydroxyphenylalanine, the rate limiting step in the biosynthesis of catecholamines (dopamine, noradrenaline and adrenaline), functioning as hormones and neurotransmitters. The enzyme is not regulated by its amino acid substrate, but instead by phosphorylation at several serine residues located N-terminal of the ACT domain, and by feedback inhibition by catecholamines at the active site. Members of this CD belong to the superfamily of ACT regulatory domains.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 444909167  10 ENKDHSSERGRVTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISREQLN 77
Cdd:cd04930   31 EEKEGKAVPQKATLLFSLKEGFSSLSRILKVFETFEAKIHHLESRPSRKEGGDLEVLVRCEVHRSDLL 98

ACT domain; This family of domains generally have a regulatory role. ACT domains are linked to a wide range of metabolic enzymes that are regulated by amino acid concentration. Pairs of ACT domains bind specifically to a particular amino acid leading to regulation of the linked enzyme. The ACT domain is found in: D-3-phosphoglycerate dehydrogenase EC:1.1.1.95, which is inhibited by serine. Aspartokinase EC:2.7.2.4, which is regulated by lysine. Acetolactate synthase small regulatory subunit, which is inhibited by valine. Phenylalanine-4-hydroxylase EC:1.14.16.1, which is regulated by phenylalanine. Prephenate dehydrogenase EC:4.2.1.51. formyltetrahydrofolate deformylase EC:3.5.1.10, which is activated by methionine and inhibited by glycine. GTP pyrophosphokinase EC:2.7.6.5

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 444909167   21 VTLIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNSEFEIFVDCDISR-----EQLNDIF 80
Cdd:pfam01842   1 TVLEVLVPDRPGLLARVLGALADRGINITSIEQGTSEDKGGIVFVVIVVDEEDleevlEALKKLE 65

ACT domains are commonly involved in specifically binding an amino acid or other small ligand leading to regulation of the enzyme; Members of this CD belong to the superfamily of ACT regulatory domains. Pairs of ACT domains are commonly involved in specifically binding an amino acid or other small ligand leading to regulation of the enzyme. The ACT domain has been detected in a number of diverse proteins; some of these proteins are involved in amino acid and purine biosynthesis, phenylalanine hydroxylation, regulation of bacterial metabolism and transcription, and many remain to be characterized. ACT domain-containing enzymes involved in amino acid and purine synthesis are in many cases allosteric enzymes with complex regulation enforced by the binding of ligands. The ACT domain is commonly involved in the binding of a small regulatory molecule, such as the amino acids L-Ser and L-Phe in the case of D-3-phosphoglycerate dehydrogenase and the bifunctional chorismate mutase-prephenate dehydratase enzyme (P-protein), respectively. Aspartokinases typically consist of two C-terminal ACT domains in a tandem repeat, but the second ACT domain is inserted within the first, resulting in, what is normally the terminal beta strand of ACT2, formed from a region N-terminal of ACT1. ACT domain repeats have been shown to have nonequivalent ligand-binding sites with complex regulatory patterns such as those seen in the bifunctional enzyme, aspartokinase-homoserine dehydrogenase (ThrA). In other enzymes, such as phenylalanine hydroxylases, the ACT domain appears to function as a flexible small module providing allosteric regulation via transmission of conformational changes, these conformational changes are not necessarily initiated by regulatory ligand binding at the ACT domain itself. ACT domains are present either singularly, N- or C-terminal, or in pairs present C-terminal or between two catalytic domains. Unique to cyanobacteria are four ACT domains C-terminal to an aspartokinase domain. A few proteins are composed almost entirely of ACT domain repeats as seen in the four ACT domain protein, the ACR protein, found in higher plants; and the two ACT domain protein, the glycine cleavage system transcriptional repressor (GcvR) protein, found in some bacteria. Also seen are single ACT domain proteins similar to the Streptococcus pneumoniae ACT domain protein (uncharacterized pdb structure 1ZPV) found in both bacteria and archaea. Purportedly, the ACT domain is an evolutionarily mobile ligand binding regulatory module that has been fused to different enzymes at various times.

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                 ....*....|....*....|....*....|....*....|....*....|..
gi 444909167  23 LIFSLENEVGGLIKVLKIFQENHVSLLHIESRKSKQRNsEFEIFVDCDISRE 74
Cdd:cd02116    1 LTVSGPDRPGLLAKVLSVLAEAGINITSIEQRTSGDGG-EADIFIVVDGDGD 51