Taxonomic distribution of proteins containing ALAD domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing ALAD domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Synthesis of bisubstrate inhibitors of porphobilinogen synthase fromPseudomonas aeruginosa.

Gacond S, Frere F, Nentwich M, Faurite JP, Frankenberg-Dinkel N, Neier R
Chem Biodivers. 2007; 4: 189-202

Porphobilinogen synthase (PBGS) synthesizes porphobilinogen 2 (PBG), thecommon precursor of all natural tetrapyrroles, through an asymmetriccondensation of two molecules of 5-aminolevulinic acid 1 (ALA).Symmetrically linked dimers 7-11 derived from levulinic acid 3(gamma-oxovaleric acid) have been synthesized to mimic the assumedbisubstrate bound to the active site of the enzyme. Their inhibitionpotential was characterized by determination of the IC(50) and K(i) valuesusing PBGS from Pseudomonas aeruginosa. The polarity and the size of thefunctional group linking the two levulinic acid 3 units have a stronginfluence on the inhibition behavior.

ALAD porphyria is a conformational disease.

Jaffe EK, Stith L
Am J Hum Genet. 2007; 80: 329-37

ALAD porphyria is a rare porphyric disorder, with five documented compoundheterozygous patients, and it is caused by a profound lack ofporphobilinogen synthase (PBGS) activity. PBGS, also called"delta-aminolevulinate dehydratase," is encoded by the ALAD gene andcatalyzes the second step in the biosynthesis of heme. ALAD porphyria is arecessive disorder; there are two common variant ALAD alleles, whichencode K59 and N59, and eight known porphyria-associated ALAD mutations,which encode F12L, E89K, C132R, G133R, V153M, R240W, A274T, and V275M.Human PBGS exists as an equilibrium of functionally distinct quaternarystructure assemblies, known as "morpheeins," in which one functionalhomo-oligomer can dissociate, change conformation, and reassociate into adifferent oligomer. In the case of human PBGS, the two assemblies are ahigh-activity octamer and a low-activity hexamer. The current studyquantifies the morpheein forms of human PBGS for the common andporphyria-associated variants. Heterologous expression in Escherichiacoli, followed by separation of the octameric and hexameric assemblies onan ion-exchange column, showed that the percentage of hexamer for F12L(100%), R240W (80%), G133R (48%), C132R (36%), E89K (31%), and A274T (14%)was appreciably larger than for the wild-type proteins K59 and N59 (0% and3%, respectively). All eight porphyria-associated variants, includingV153M and V275M, showed an increased propensity to form the hexamer,according to a kinetic analysis. Thus, all porphyria-associated human PBGSvariants are found to shift the morpheein equilibrium for PBGS toward theless active hexamer. We propose that the disequilibrium of morpheeinassemblies broadens the definition of conformational diseases beyond theprion disorders and that ALAD porphyria is the first example of amorpheein-based conformational disease.

Identification of lysine at the active site of human 5-aminolaevulinatedehydratase.

Gibbs PN, Jordan PM
Biochem J. 1986; 236: 447-51

Reduction of human 5-aminolaevulinate dehydratase with NaBH4 in thepresence of 14C-labelled substrate led to complete loss of catalyticactivity and to incorporation of label into the enzyme protein. Bycomparison with authentic lysyl-aminolaevulinic acid, prepared chemically,the modified active-site amino acid obtained by acid hydrolysis was shownto be lysine. Sequencing of a CNBr-cleavage peptide isolated from theinactivated 14C-labelled enzyme revealed that the lysine was presentwithin the sequence M-V-K-P-G-M.