Aminolevulinic acid: from its unique biological function to its star role in photodynamic therapy

Fukuda, Haydée; Casas, Adriana; Batlle, Alcira

doi:10.1016/j.biocel.2004.04.018

Cited by 121 publications

(77 citation statements)

References 14 publications

(9 reference statements)

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“…Besides shedding light on the mechanism of ALA production, hyperactive ALASs might also find philanthropic utility in the generation of ALA for a variety of clinical and agricultural applications (4,(12)(13)(14). To test our hypothesis, we employed synthetic mixed base oligonucleotides to generate a library of ALAS loop variants, coupled with a simple screening strategy to isolate potentially hyperactive clones.…”

Section: Aminolevulinate (Ala)mentioning

confidence: 99%

Targeting the Active Site Gate to Yield Hyperactive Variants of 5-Aminolevulinate Synthase

Lendrihas

Hunter

Ferreira

2010

Journal of Biological Chemistry

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The rate of porphyrin biosynthesis in mammals is controlled by the activity of the pyridoxal 5-phosphate-dependent enzyme 5-aminolevulinate synthase (EC 2.3.1.37). Based on the postulate that turnover in this enzyme is controlled by conformational dynamics associated with a highly conserved active site loop, we constructed a variant library by targeting imperfectly conserved noncatalytic loop residues and examined the effects on product and porphyrin production. Functional loop variants of the enzyme were isolated via genetic complementation in Escherichia coli strain HU227. Colony porphyrin fluorescence varied widely when bacterial cells harboring the loop variants were grown on inductive media; this facilitated identification of clones encoding unusually active enzyme variants. Nine loop variants leading to high in vivo porphyrin production were purified and characterized kinetically. Steady state catalytic efficiencies for the two substrates were increased by up to 100-fold. Presteady state single turnover reaction data indicated that the second step of quinonoid intermediate decay, previously assigned as reaction rate-limiting, was specifically accelerated such that in three of the variants this step was no longer kinetically significant. Overall, our data support the postulate that the active site loop controls the rate of product and porphyrin production in vivo and suggest the possibility of an as yet undiscovered means of allosteric regulation. Aminolevulinate (ALA)2 is the universal building block of tetrapyrolle biosynthesis (1). In nonplant eukaryotes and the ␣-subclass of purple bacteria, the production of ALA is catalyzed by the pyridoxal 5Ј-phosphate (PLP)-dependent enzyme 5-aminolevulinate synthase (ALAS) (EC 2.3.1.37), in a reaction involving the Claisen-like condensation of succinyl-coenzyme-A and glycine to yield CoA, carbon dioxide, and ALA (2). ALAS catalyzes the first committed step of tetrapyrrole biosynthesis in these organisms, which is also the rate-determining step of the pathway. Consequently, overexpression of ALAS in prokaryotic and eukaryotic cells results in accumulation of the photosensitizing heme precursor protoporphyrin IX (3). This property could potentially lead to novel applications of ALAS or ALAS variants in photodynamic therapy of tumors and other dysplasias (4).ALAS is classified as a fold-type I PLP-dependent enzyme and, like the evolutionarily related L-amino acid transaminases (5), functions as a homodimer wherein a PLP cofactor is bound at each of the two active sites, which are recessed in clefts at the subunit interface (6, 7). X-ray crystal structures of ALAS from Rhodobacter capsulatus and the closely related enzyme 8-amino-7-oxononanoate synthase from Escherichia coli reveal an induced fit type mechanism wherein binding of substrates and product, respectively, trigger closure of an extended loop over the active site (6, 8) (Fig. 1). The inferred conformational dynamics of this loop are of interest because kinetic and crystallographic studies support the hypothes...

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Section: Aminolevulinate (Ala)mentioning

confidence: 99%

Targeting the Active Site Gate to Yield Hyperactive Variants of 5-Aminolevulinate Synthase

Lendrihas

Hunter

Ferreira

2010

Journal of Biological Chemistry

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“…Necrosis usually occurs only in response to a pathologic form of cellular injury. Oxidative stress causes damage to cellular (macro)molecules such as nucleic acids, proteins and lipids [1][2][3][4]. This is two steps process process, where the photosensitizer absorbs a photon of light in the ground state and this promotes the PS to the short-live excited state.…”

Section: Introductionmentioning

confidence: 99%

“…ALA is particularly effective in dermatology for treating neoplastic cutaneous tissues [4]. Other examples are porphycenes [6,17] and phthalocyanines [6,[18][19][20], which are suitable PS due to their intense absorption in the red, high triplet state quantum yields and long triplet lifetimes.…”

Section: Introductionmentioning

confidence: 99%

Nanodrug applications in photodynamic therapy

Paszko

Ehrhardt

Senge

et al. 2011

Photodiagnosis and Photodynamic Therapy

326

215

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SummaryPhotodynamic therapy (PDT) has developed over last century and is now becoming a more widely used medical tool having gained regulatory approval for the treatment of various diseases such as cancer and macular degeneration. It is a two-step technique in which delivery of a photosensitizing drug is followed by irradiation of light. Activated photosensitizers transfer energy to molecular oxygen which results in generation of reactive oxygen species which in turn cause cells apoptosis or necrosis. Although this modality has significantly improved quality of life and survival time for many cancer patients it still offers significant potential for further improvement. In addition to the development of new PDT drugs, the use of nanosized carriers for photosensitizers is a promising approach which might improve the efficiency of photodynamic activity and which can overcome many side effects associated with classic photodynamic therapy. This review aims at highlighting the different types of nanomedical approaches currently used in PDT and outlines future trends and limitations of nanodelivery of photosensitizers. PDT -photodynamic therapy; PGA -poly(glycolic acid); PGLA -poly(D,L-lactide-coglycolide); PLA -poly(lactic acid); PS -photosensitizer; PEG -polyethylene glycol; ALA  aminolevulinic acid; m-THPC  5,10,15,20-tetra-(m-hydroxyphenyl)chlorine; m-THPP  meso-tetra(p-hydroxyphenyl); PpIX  protoporphyrin; Hp  hematoporphyrin; Pc4  silicon phthalocyanine; Ig  immunoglobulin; Tf  transferrin; TfR  transferrin receptor; VEGF  vascular endothelial growth factor; EPR  enhanced permeability and retention effect; FRET  fluorescence resonance energy transfer; MRI  magnetic resonance imaging; RES  reticuloendothelial system; ROS  reactive oxygen species; NP  nanoparticle; ND -nanodiamonds; SNP  silica nanoparticle; AMD  age-related macular degeneration; CNV  choroidal neovascularization; PTT  photothermal therapy;

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“…ALA and MAL are two of the most used endogenous photosensitizers and are precursors of PpIX, a high photosensitive product (23). As it is known, parasites of the genus Leishmania lack several of the enzymes involved in the PpIX synthesis and treatment with ALA or MAL will not produce a phototoxic effect after PDT (24).…”

Section: Discussionmentioning

confidence: 99%

“…After several enzymatic reactions, it leads to the formation of the heme group through the incorporation of Fe ++ into PpIX by the action of a ferrochelatase enzyme. Since the rate of ALA formation is regulated by the amount of the concentration of the produced heme (by downregulation of transcription and translocation of the enzyme ALA synthase), when ALA is administrated externally, in the case of ALA-PDT (at 570-670 nm), the feedback regulation is bypassed, the capacity of the ferrochelatase enzyme to attach iron decreases and a higher concentration of PpIX is accumulated inside the cells becoming a powerful photosensitizer for PDT (23).…”

mentioning

confidence: 99%

Acumulación celular y el efecto de anti-Leishmania de protoporfirina IX exógena y endógena después del tratamiento fotodinámico

Mateus¹,

Valdivieso²,

Hernández³

et al. 2014

biomedica

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participated in the design and development of the in vitro assays, cell culture, confocal microscopy, drug screening and statistical analysis. Fernando Martínez and Edgar Páez participated in compound characterization and spectrophotometric tests of the stability of PpIX solutions. Patricia Escobar directed the research, designed the protocols and led the statistical analysis and results interpretation. All authors contributed in the analysis and writing of the article.

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Aminolevulinic acid: from its unique biological function to its star role in photodynamic therapy

Cited by 121 publications

References 14 publications

Targeting the Active Site Gate to Yield Hyperactive Variants of 5-Aminolevulinate Synthase

Targeting the Active Site Gate to Yield Hyperactive Variants of 5-Aminolevulinate Synthase

Nanodrug applications in photodynamic therapy

Acumulación celular y el efecto de anti-Leishmania de protoporfirina IX exógena y endógena después del tratamiento fotodinámico

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