Monounsaturated fatty acids (MUFA) are emerging health biomarkers, and in particular the ratio between palmitoleic acid (9cis-16:1) and palmitic acid (16:0) affords the delta-9 desaturase index that is increased in obesity. Recently, other positional and geometrical MUFA isomers belonging to the hexadecenoic family (C16 MUFA) were found in circulating lipids, such as sapienic acid (6cis-16:1), palmitelaidic acid (9trans-16:1) and 6trans-16:1. In this work we report: i) the identification of sapienic acid as component of human erythrocyte membrane phospholipids with significant increase in morbidly obese patients (n = 50) compared with age-matched lean controls (n = 50); and ii) the first comparison of erythrocyte membrane phospholipids (PL) and plasma cholesteryl esters (CE) in morbidly obese patients highlighting that some of their fatty acid levels have opposite trends: increases of both palmitic and sapienic acids with the decrease of linoleic acid (9cis,12cis-18:2, omega-6) in red blood cell (RBC) membrane PL were reversed in plasma CE, whereas the increase of palmitoleic acid was similar in both lipid species. Consequentially, desaturase enzymatic indexes gave different results, depending on the lipid class used for the fatty acid content. The fatty acid profile of morbidly obese subjects also showed significant increases of stearic acid (C18:0) and C20 omega-6, as well as decreases of oleic acid (9cis-18:1) and docosahexaenoic acid (C22:6 omega-3) as compared with lean healthy controls. Trans monounsaturated and polyunsaturated fatty acids were also measured and found significantly increased in both lipid classes of morbidly obese subjects. These results highlight the C16 MUFA isomers as emerging metabolic marker provided that the assignment of the double bond position and geometry is correctly performed, thus identifying the corresponding lipidomic pathway. Since RBC membrane PL and plasma CE have different fatty acid trends, caution must also be used in the choice of lipid species for the interpretation of lipidomic profiles.

A poly(ADP-ribose) polymerase-like enzyme, detected in a crude homogenate from Sulfolobus solfataricus by means of activity and immunoblot analyses, was purified to electrophoretic homogeneity by a rapid procedure including two sequential affinity chromatographies, on NAD⁺-agarose and DNA-Sepharose. The latter column selected specifically the poly(ADP-ribosyl)ating enzyme with a 17% recovery of enzymic activity and a purification of more than 15000-fold. The molecular mass (54–55 kDa) assessed by SDS/PAGE and immunoblot was definitely lower than that determined for the corresponding eukaryotic protein. The enzyme was proved to be thermophilic, with a temperature optimum of approx. 80 °C, and thermostable, with a half-life of 204 min at 80 °C, in good agreement with the requirements of a thermozyme. It displayed a K_m towards NAD⁺ of 154±50 µM; in the pH range 6.5–10.0 the activity values were similar, not showing a real optimum pH. The enzyme was able to bind homologous DNA, as evidenced by the ethidium bromide displacement assay. The product of the ADP-ribosylating reaction co-migrated with the short oligomers of ADP-ribose (less than 6 residues) from a eukaryotic source. Reverse-phase HPLC analysis of the products, after digestion with phosphodiesterase I, gave an elution profile reproducing that obtained by the enzymic digestion of the rat testis poly(ADP-ribose). These results strongly suggest that the activities of the purified enzyme include the elongation step.

Epigenetic states that allow chromatin fidelity inheritance can be mediated by several factors. One of them, histone variants and their modifications (including acetylation, methylation, phosphorylation, poly(ADP-ribosyl)ation, and ubiquitylation) create distinct patterns of signals read by other proteins, and are strictly related to chromatin remodelling, which is necessary for the specific expression of a gene, and for DNA repair, recombination, and replication. In the framework of chromatin-controlling factors, the poly(ADP-ribosyl)ation of nuclear proteins, catalysed by poly(ADP-ribose)polymerases (PARPs), has been implicated in the regulation of both physiological and pathological events (gene expression/amplification, cellular division/differentiation, DNA replication, malignant transformation, and apoptotic cell death). The involvement of PARPs in this scenario has raised doubts about the epigenetic value of poly(ADP-ribosyl)ation, because it is generally activated after DNA damage. However, one emerging view suggests that both the product of this reaction, poly(ADP-ribose), and PARPs, particularly PARP 1, play a fundamental role in recruiting protein targets to specific sites and (or) in interacting physically with structural and regulatory factors, through highly reproducible and inheritable mechanisms, often independent of DNA breaks. The interplay of PARPs with protein factors, and the combinatorial effect of poly(ADPribosyl)ation with other post-translational modifications has shed new light on the potential and versatility of this dynamic reaction.Key words: chromatin, epigenetic, poly(ADP-ribose), PARP.