Abstract
NAD+ has emerged as a crucial element in both bioenergetic and signaling pathways since it acts as a key regulator of cellular and organism homeostasis. NAD+ is a coenzyme in redox reactions, a donor of adenosine diphosphate-ribose (ADPr) moieties in ADP-ribosylation reactions, a substrate for sirtuins, a group of histone deacetylase enzymes that use NAD+ to remove acetyl groups from proteins; NAD+ is also a precursor of cyclic ADP-ribose, a second messenger in Ca++ release and signaling, and of diadenosine tetraphosphate (Ap4A) and oligoadenylates (oligo2′-5′A), two immune response activating compounds. In the biological systems considered in this review, NAD+ is mostly consumed in ADP-ribose (ADPr) transfer reactions. In this review the roles of these chemical products are discussed in biological systems, such as in animals, plants, fungi and bacteria. In the review, two types of ADP-ribosylating enzymes are introduced as well as the pathways to restore the NAD+ pools in these systems.
Highlights
NAD+ has emerged as a dual faced compound, present in all the kingdoms of life, being a cofactor in metabolic pathways and redox reactions, and a substrate used by enzymes involved in post-translational modifications, in particular in deacetylation reactions, and in ADP ribosylation reactions, producing mono ADP ribose (MAR) and poly ADP ribose (PAR) moieties bound to proteins and nucleic acids [1,2,3,4,5,6]
Studying Arabidopsis, Rissel and colleagues showed that poly ADP-ribose polymerase (PARP) domain proteins (RCD1, SRO1, and its paralogues) still contribute to protect the plant from biotic stress through PAR modification, while levels of protein PARylation even increased in the parp-/- triple mutant
Pétriacq and colleagues used the nadC gene derived from E. coli expressed in Arabidopsis; they reported that higher NAD+ contents in nadC-overexpressing plants with the addition of quinolinate activated the plant immune response and resulted in disease resistance against a virulent bacterial pathogen, P, syringae pv. tomato, harboring the Pst-AvrRpm1 avirulence factor [85]
Summary
NAD+ has emerged as a dual faced compound, present in all the kingdoms of life, being a cofactor in metabolic pathways and redox reactions, and a substrate used by enzymes involved in post-translational modifications, in particular in deacetylation reactions, and in ADP ribosylation reactions, producing mono ADP ribose (MAR) and poly ADP ribose (PAR) moieties bound to proteins and nucleic acids [1,2,3,4,5,6]. The complex of modification enzymes, in addition to writers and erasers, includes the readers and proteins that bind to MAR or to PAR segments, interacting with specific domains [5] (Figure 1). MAR binding (readers), while other proteins have pathogens, eraser activity: macrodomains infecting eukaryotic cells, as well as plant produce toxins thatcarrying promote glycohydrolase activity can release the MAR/PAR from the modified amino acid of the bacterial infections. The majority of ADP-ribosylating belong mono-ADP-ribosyl transferase reported to be enzymatically inactive, forms heterodimers with to the poly ADP-ribose polymerase (PARP)/diphteria toxin-type ADP-ribosyl transferase (ARTD). Signaling and immunity, Very few organisms are devoid of the enzymes involved in PAR synthesis and degradation Such as MAPKKs, GTP Exchange Factors (GEF) and RNA binding proteins [16,17].
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