Catabolism of the Lipofuscin Cycloretinal by MsP1
Irum Perveen1, Brett A Johnson1, Vishruth Gowda1
1Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.
Abstract:
Age-related macular degeneration (AMD) is a debilitating eye disease that tends to affect people over the age of 55. Lipofuscins are autofluorescent, toxic byproducts of the visual cycle thought to contribute toward the progression of the disease. Targeting the accumulation of lipofuscin through catabolism may serve as a method for the early treatment of AMD. Thus, an enzymatic approach capable of degrading lipofuscin, cycloretinal (all-trans retinal dimer), was examined. A peroxidase from the organism Marasmius scorodonius (MsP1) has shown capability of degrading this toxic metabolite into nontoxic byproducts. A catalytic triad within MsP1 (D228, H365, and R388) was identified through multiple-sequence alignment and homology modeling and confirmed by kinetic analysis. MsP1-associated cleavage products were detected by gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and liquid chromatography-tandem mass spectrometry (LC-MSMS). MsP1 degradation byproducts of cycloretinal show reduced cytotoxicity within cell culture (ARPE-19), demonstrating its potential as a gene therapeutic to alleviate the buildup of lipofuscin within AMD.
Insights
A novel enzyme, Marasmius scorodonius peroxidase 1 (MsP1), degrades toxic lipofuscin buildup implicated in age-related macular degeneration (AMD). This enzymatic approach offers a potential gene therapy for early AMD treatment by reducing cellular toxicity.
Area of Science:
- Biochemistry and Molecular Biology
- Ophthalmology
- Enzymology
Background:
- Age-related macular degeneration (AMD) is an eye disease affecting individuals over 55.
- Lipofuscins, toxic byproducts of the visual cycle, accumulate and contribute to AMD progression.
- Targeting lipofuscin catabolism presents a potential early treatment strategy for AMD.
Purpose of the Study:
- To investigate the enzymatic degradation of cycloretinal, a lipofuscin precursor.
- To evaluate the potential of Marasmius scorodonius peroxidase 1 (MsP1) for lipofuscin breakdown.
- To assess the therapeutic implications of MsP1 in mitigating AMD pathology.
Main Methods:
- Identification of a catalytic triad (D228, H365, R388) in MsP1 using sequence alignment and homology modeling.
- Confirmation of catalytic activity through kinetic analysis.
- Analysis of MsP1-mediated cycloretinal cleavage products using GC-MS, HPLC, LC-MS, and LC-MSMS.
Main Results:
- MsP1 effectively degrades cycloretinal into non-toxic byproducts.
- The catalytic triad within MsP1 is crucial for its enzymatic activity.
- Degradation products exhibited reduced cytotoxicity in ARPE-19 cell cultures.
Conclusions:
- MsP1 demonstrates significant potential as an enzyme for lipofuscin degradation.
- The reduced cytotoxicity of MsP1 byproducts supports its therapeutic application.
- MsP1 represents a promising candidate for gene therapy aimed at alleviating lipofuscin accumulation in AMD.
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