Folding and unfolding of δ-aminolevulinic acid dehydratase and porphobilinogen deaminase induced by uro- and protoporphyrin

Afonso, Susana; Salamanca, Rafael Enrı́quez de; Batlle, Alcira

doi:10.1016/s1357-2725(96)00093-3

Cited by 9 publications

(6 citation statements)

References 41 publications

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“…It was found that ALA-D was always more affected than PBG-D, and the action of URO I action was greater than that exerted by PROTO IX (53).…”

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 93%

“…Tryptic digestion of liver ALA-D and PBG-D exposed to URO I or PROTO IX resulted in an increase of protein degradation products. This effect was stronger when enzymes were exposed to porphyrins under UV light (53).…”

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 95%

“…In high salt solution, repulsion of hydrophobic groups by the solvent cage is maximized (52). Enzyme solubility of liver ALA-D and PBG-D in buffer containing 3 M KCl decreased with increasing time of treatment in the presence of URO I or PROTO IX, suggesting that porphyrins were interacting with the protein structure, exposing hydrophobic residues which are shielded in the core of the protein in its native configuration (53). These changes were observed when treatment was performed either under UV light or in the dark, although enzyme solubility was more affected in the former condition.…”

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 96%

“…An increased susceptibility to proteolysis of a wide variety of proteins upon their exposure to hydroxyl radicals in vitro has been demonstrated (53,55). Tryptic digestion of liver ALA-D and PBG-D exposed to URO I or PROTO IX resulted in an increase of protein degradation products.…”

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 99%

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The photodynamic and non-photodynamic actions of porphyrins

Afonso

Salamanca

Batlle

1999

Braz J Med Biol Res

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Porphyrias are a family of inherited diseases, each associated with a partial defect in one of the enzymes of the heme biosynthetic pathway. In six of the eight porphyrias described, the main clinical manifestation is skin photosensitivity brought about by the action of light on porphyrins, which are deposited in the upper epidermal layer of the skin. Porphyrins absorb light energy intensively in the UV region, and to a lesser extent in the long visible bands, resulting in transitions to excited electronic states. The excited porphyrin may react directly with biological structures (type I reactions) or with molecular oxygen, generating excited singlet oxygen (type II reactions). Besides this well-known photodynamic action of porphyrins, a novel light-independent effect of porphyrins has been described. Irradiation of enzymes in the presence of porphyrins mainly induces type I reactions, although type II reactions could also occur, further increasing the direct non-photodynamic effect of porphyrins on proteins and macromolecules. Conformational changes of protein structure are induced by porphyrins in the dark or under UV light, resulting in reduced enzyme activity and increased proteolytic susceptibility. The effect of porphyrins depends not only on their physico-chemical properties but also on the specific site on the protein on which they act. Porphyrin action alters the functionality of the enzymes of the heme biosynthetic pathway exacerbating the metabolic deficiencies in porphyrias. Light energy absorption by porphyrins results in the generation of oxygen reactive species, overcoming the protective cellular mechanisms and leading to molecular, cell and tissue damage, thus amplifying the porphyric picture.

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“…It was found that ALA-D was always more affected than PBG-D, and the action of URO I action was greater than that exerted by PROTO IX (53).…”

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 93%

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 95%

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 96%

Section: Molecular Alterations Induced By Porphyrinsmentioning

confidence: 99%

See 2 more Smart Citations

The photodynamic and non-photodynamic actions of porphyrins

Afonso

Salamanca

Batlle

1999

Braz J Med Biol Res

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“…Albeit their clinical significance, the biochemical mechanism behind the accumulation of metabolites associated with acute porphyrias has not been experimentally demonstrated. It has been shown that some porphyrins are able to in vitro inactivate the ALAD enzyme. , Moreover, ALAD condensation reaction stalls at a covalently bound intermediate that resembles the product, so ALAD inhibition by PBG seems plausible. Alternatively, an excess of PBG could also inhibit PBGD, providing an alternative explanation for the metabolite accumulation.…”

Section: Introductionmentioning

confidence: 99%

ALAD Inhibition by Porphobilinogen Rationalizes the Accumulation of δ-Aminolevulinate in Acute Porphyrias

et al. 2022

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Patients with major forms of acute hepatic porphyria present acute neurological attacks with overproduction of porphobilinogen (PBG) and δ-aminolevulinic acid (ALA). Even if ALA is considered the most likely agent inducing the acute symptoms, the mechanism of its accumulation has not been experimentally demonstrated. In the most frequent form, acute intermittent porphyria (AIP), inherited gene mutations induce a deficiency in PBG deaminase; thus, accumulation of the substrate PBG is biochemically obligated but not that of ALA. A similar scenario is observed in other forms of acute hepatic porphyria (i.e., porphyria variegate, VP) in which PBG deaminase is inhibited by metabolic intermediates. Here, we have investigated the molecular basis of δ-aminolevulinate accumulation using in vitro fluxomics monitored by NMR spectroscopy and other biophysical techniques. Our results show that porphobilinogen, the natural product of δaminolevulinate deaminase, effectively inhibits its anabolic enzyme at abnormally low concentrations. Structurally, this high affinity can be explained by the interactions that porphobilinogen generates with the active site, most of them shared with the substrate. Enzymatically, our flux analysis of an altered heme pathway demonstrates that a minimum accumulation of porphobilinogen will immediately trigger the accumulation of δ-aminolevulinate, a long-lasting observation in patients suffering from acute porphyrias.

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Protoporphyrin IX-induced structural and functional changes in human red blood cells, haemoglobin and myoglobin

et al. 2004

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Protoporphyrin IX and its derivatives are used as photosensitizers in the photodynamic therapy of cancer. Protoporphyrin IX penetrates into human red blood cells and releases oxygen from them. This leads to a change in the morphology of the cells. Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes. For both proteins, the binding affinity constant decreases, while the possible number of binding sites increases, as the aggregation state of the porphyrin is increased. The interactions lead to conformational changes of both haemoglobin and myoglobin as observed in circular dichroism studies. Upon binding with the proteins, protoporphyrin IX releases the heme-bound oxygen from the oxyproteins, which is dependent on the stoichiometric ratios of the porphyrin : protein. The peroxidase activities of haemoglobin and myoglobin are potentiated by the protein-porphyrin complexation. Possible mechanisms underlying the relation between the porphyrin-induced structural modifications of the heme proteins and alterations in their functional properties have been discussed. The findings may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.

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Folding and unfolding of δ-aminolevulinic acid dehydratase and porphobilinogen deaminase induced by uro- and protoporphyrin

Cited by 9 publications

References 41 publications

The photodynamic and non-photodynamic actions of porphyrins

The photodynamic and non-photodynamic actions of porphyrins

ALAD Inhibition by Porphobilinogen Rationalizes the Accumulation of δ-Aminolevulinate in Acute Porphyrias

Protoporphyrin IX-induced structural and functional changes in human red blood cells, haemoglobin and myoglobin

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