Biology subjects

Pey, A. l.

Publications and source records attributed to Pey, A. l..

3 recordsLinked to original sources

bioRxiv2025

Phosphorylation of Ser81 in human AGT reversibly inactivate enzyme function and mimics catalytic defects of certain PH1-causing mutations

Phosphorylation is fundamental to modulate protein function and stabilty. There have detected about 300000 site-specic Phosphorylation sites in over 20000 human proteins. However, only 5% of the sites have been experimenrally characterized. In this work, we investigated a phosphorylation event in AGT, an important enzyme due to its detoxifying role of glyoxylate and hundreds of mutations cause a rare disease (primary hyperoxaluria type I or PH1). We analyzed the effect of phosphomimetic mutations Ser81 on the WT proten, the common polymorpshim LM, and the most common disease-associted variants (LM-G170R and LM-I244T). Using biochemical, biophysical and cell biology approaches, we show that phosphorylation at S81 dramatically affects PLP/PMP binding pose and disrupts enzyme activity, without pertubing its subcellular location to peroxisomes. This reversible phenotype is similar to the irreversible effects of some PH1-causing mutaions. Thus, we provide evidence for a novel regulatory mechanism for PH1, in health and disease.

biophysics↗

bioRxiv2025

Nanobodies as therapies for loss-of-function misfolding diseases.

Misfolding diseases that result in loss of function represent a considerable burden for both individuals and society. Primary hyperoxaluria type 1 (PH1) is a rare genetic disorder caused by mutations in the alanine:glyoxylate aminotransferase 1 (AGT) enzyme. The underlying molecular mechanisms causing PH1 are associated with protein misfolding (enhanced aggregation and mitochondrial mistargeting). The main therapeutic approach to increase patients lifespan and quality of life is a double kidney and liver transplantation. Alternative treatments such as gene and enzyme replacement and pharmacological chaperones are currently being introduced, but other alternatives are necessary. In this work, we developed and characterized a novel biotechnological approach using six single-domain nanobodies (NB-AGT-1 to -6) as potential therapeutics for PH1 misfolding. We show that NB-AGTs are very stable proteins and bind to pathogenic and non-pathogenic variants of AGT with extreme affinities (with Kd values from low nM to low pM). Structural studies showed that NB-AGTs bind to different epitopes of AGT with selectivity for different AGT variants. Experiments in cellular PH1 models showed that internalization of engineered NB-AGT-3 enhanced the specific activity of disease-associated variants. Overall, we show that NBs are a novel and promising approach to treat PH1 and other loss-of-function misfolding diseases.

biophysics↗

bioRxiv2025

Active site tyrosine residues in human NQO1 homodimer are critical for non-synchronous enzyme catalysis at the two active sites.

AbstractHuman NQO1 is a flavoenzyme essential for the redox metabolization of many substances and associated with wide-impacting diseases such as cancer and Alzheime[r]s. Recent X-ray crystallographic studies have proposed that a few residues at the active site of NQO1 (including Tyr126 and Tyr128) may control enzyme catalysis and functional negative cooperativity. In this work, we use rapid mixing pre-steady state kinetics and hydrogen-deuterium exchange followed by mass spectrometry (HDX-MS) to evaluate experimentally the role of Tyr126 and Tyr128 in NQO1 functionality by generating mutants to Phe, Ala and Glu. Mutations to Phe caused mild effects, whereas those to Ala significantly decreased hydride transfer efficiency and those to Glu virtually abolished NQO1 activity. Interestingly, structural stability studies by HDX-MS showed significant perturbations particularly affecting the binding site of NADH/NAD+ in the less conservative mutations (particularly to Glu). Mutations of Tyr126 and Tyr128 seem to also modulate the non-synchronous catalysis in the two active sites (negative cooperativity) as well as the selectivity for NADH/NADPH as coenzymes. Our work experimentally demonstrates the critical role of Tyr126 and Tyr128 in the flavin reductive half-reaction of the catalytic cycle of NQO1 in the negative cooperativity, and also suggests that phosphorylation of these two Tyr residues might shut down NQO1 activity reversibly.

biophysics↗