The occurrence of riboflavin kinase and FAD synthetase ensures FAD synthesis in tobacco mitochondria and maintenance of cellular redox status

The Occurrence Of Riboflavin Kinase And FAD Synthetase Ensures FAD Synthesis In Tobacco Mitochondria And Maintenance Of Cellular Redox Status

Authors:

Teresa A. Giancaspero, Vittoria Locato, Maria C. de Pinto, Laura De Gara, Maria Barile

Field:

Biochemistry and Molecular Biology

Document Content:

This study investigates how tobacco mitochondria (cv. Bright Yellow 2) acquire and utilize riboflavin (Rf) to synthesize flavin adenine dinucleotide (FAD), a crucial cofactor for cellular redox balance. Intact mitochondria demonstrate carrier-mediated uptake of Rf with varying efficiencies. Once inside, Rf is converted to active cofactors FMN and FAD by mitochondrial riboflavin kinase and FAD synthetase. Newly synthesized FAD can also be exported. The study highlights the dependence of FMN synthesis on Rf concentration and the activation of FAD-forming enzymes by MgCl2. These enzymes, riboflavin kinase and FAD synthetase, exist as distinct monofunctional entities within mitochondrial soluble and membrane-enriched fractions, respectively. While mammals require dietary riboflavin, plants, fungi, and bacteria can synthesize it de novo. Riboflavin’s primary role is its conversion into FMN and FAD, essential for numerous dehydrogenases, reductases, and oxidases. These flavoenzymes are crucial for mitochondrial electron transport, photosynthesis, fatty acid metabolism, and the regeneration of reduced glutathione, thereby defending against oxidative stress and modulating protein function. In plants, FAD is also integral to ascorbate biosynthesis and recycling, playing a key role in plant defense against oxidative stress and programmed cell death. The research provides experimental evidence for Rf uptake, FAD synthesis, and FAD export in TBY-2 mitochondria, confirming the presence and functional localization of key enzymes involved in this vital metabolic pathway.

Table of Contents:

• Keywords
• Correspondence
• Abstract
• Introduction
• Results
• Experimental Procedures
• Discussion
• References