Biology subjects

Kashyap, S. N.

Publications and source records attributed to Kashyap, S. N..

2 recordsLinked to original sources

bioRxiv2025

A Novel Phosphatase Reverses the Leloir Pathway to Promote Tagatose Synthesis from Glucose

D-Tagatose is a natural, low-calorie, rare monosaccharide that has gained substantial interest as an alternative sweetener. It offers numerous benefits, including a low glycemic index, prebiotic properties, and the ability to lower blood sugar levels. Currently, tagatose is primarily produced industrially through the isomerization of galactose, utilizing both chemical and enzymatic catalysis. While these established processes can produce tagatose, they are inefficient and expensive. Recent works have demonstrated alternative biosynthetic routes to produce D-tagatose but suffer from low theoretical yield and/or reliance on expensive feedstocks. This study demonstrates a novel biochemical pathway to produce D-tagatose directly from glucose using a whole-cell process with Escherichia coli. This process is distinct from other biosynthetic schemes and utilizes a newly discovered galactose-1-phosphate-selective phosphatase to drive the native Leloir pathway in reverse and synthesize the substrate D-galactose directly from D-glucose. Our analysis of the phosphatase reveals how an ensemble of intermolecular hydrogen bonds governs substrate specificity. By co-expressing this phosphatase and an L-arabinose isomerase in a modified strain background, we demonstrate production of tagatose directly from glucose. In initial studies, we generated [~]10.5 g/L galactose from 30 g/L glucose (35 % yield) while also producing > 1 g/L tagatose. This demonstrates the feasibility of a novel approach to tagatose production in vivo with a theoretical pathway yield of 94.9 %, which is substantially higher than previously proposed tagatose biosynthetic schemes.

bioengineering↗

bioRxiv2024

Carboxy-terminal blockade of sortilin binding enhances progranulin gene therapy, a potential treatment for frontotemporal dementia

Frontotemporal dementia is commonly caused by loss-of-function mutations in the progranulin gene. Potential therapies for this disorder have entered clinical trials, including progranulin gene therapy and drugs that reduce progranulin interactions with sortilin. Both approaches ameliorate functional and pathological abnormalities in mouse models of progranulin insufficiency. Here we investigated whether modifying the progranulin carboxy terminus to block sortilin interactions would improve the efficacy of progranulin gene therapy. We compared the effects of treating progranulin-deficient mice with gene therapy vectors expressing progranulin with intact sortilin interactions, progranulin with the carboxy terminus blocked to reduce sortilin interactions, or GFP control. We found that expressing carboxy-terminally blocked progranulin generated higher levels of progranulin both at the injection site and in more distant regions. Carboxy-terminally blocked progranulin was also more effective at ameliorating microgliosis, microglial lipofuscinosis, and lipid abnormalities including ganglioside accumulation and loss of bis(monoacylglycero)phosphate lipids. Finally, only carboxy-terminally blocked progranulin reduced plasma neurofilament light chain, a biomarker of neurodegeneration, in progranulin-deficient mice. These results demonstrate that modifying the progranulin cargo to block sortilin interactions may be important for increasing the effectiveness of progranulin gene therapy. One-sentence SummaryThe effectiveness of progranulin gene therapy in models of FTD is improved by blocking the proteins carboxy terminus, which prevents sortilin binding

neuroscience↗