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A cross-kingdom Nudix enzyme that pre-empts damage in thiamin metabolism
Genes specifying the thiamin monophos¬phate phosphatase and adenylated thiazole diphosphatase steps in fungal and plant thiamin biosynthesis remain unknown, as do genes for thia¬min diphosphate (ThDP) hydrolysis in thiamin metabolism. A distinctive Nudix domain fused to thia¬min di¬phos¬phokin¬ase (Tnr3) in Schizo¬sacc¬¬h¬aromyces pombe was evaluated as a candidate for these funct¬ions. Com¬par¬¬ative genomic analysis predicted a role in thiamin metabolism, not biosyn¬th¬esis, because free-standing homologues of this Nudix dom¬ain occur not only in fungi and plants, but also in proteo¬bacteria (whose thiamin biosynthesis pathway has no adenylated thiazole or thiamin monophosph¬ate hydrolysis steps) and animals (which do not make thiamin). Supporting this prediction, recomb¬¬inant Tnr3 and its Saccharo¬myces cerevisiae, Arabid¬opsis, and maize Nudix homo¬logues lacked thiamin monophosphate phos¬phatase activity but were active against ThDP, and up to 60-fold more active against diphos¬ph¬ates of the toxic thiamin degradation pro¬ducts oxy- and oxo¬thi¬amin. Deleti¬ng the S. cere¬visiae Nudix gene (YJR142W) lower¬ed oxythiamin resistance, over-expressing it rais¬ed resist¬ance, and express¬ing its plant or bacterial counterparts restored resist-ance to the YJR142W deletant. By converting the di¬phos¬phates of damaged forms of thiamin to monophosphates, the Tnr3 Nudix domain and its homologues can pre-empt the misincor¬p¬or¬ation of damaged diphosphates into ThDP-de¬pend¬ent enzymes, and the resulting toxicity
State of the art of immunoassay methods for B-type natriuretic peptides: An update
The aim of this review article is to give an update on the state of the art of the immunoassay
methods for the measurement of B-type natriuretic peptide (BNP) and its related peptides.
Using chromatographic procedures, several studies reported an increasing number of
circulating peptides related to BNP in human plasma of patients with heart failure. These
peptides may have reduced or even no biological activity. Furthermore, other studies have
suggested that, using immunoassays that are considered specific for BNP, the precursor of the
peptide hormone, proBNP, constitutes a major portion of the peptide measured in plasma of
patients with heart failure. Because BNP immunoassay methods show large (up to 50%)
systematic differences in values, the use of identical decision values for all immunoassay
methods, as suggested by the most recent international guidelines, seems unreasonable. Since
proBNP significantly cross-reacts with all commercial immunoassay methods considered
specific for BNP, manufacturers should test and clearly declare the degree of cross-reactivity of
glycosylated and non-glycosylated proBNP in their BNP immunoassay methods. Clinicians
should take into account that there are large systematic differences between methods when
they compare results from different laboratories that use different BNP immunoassays. On the
other hand, clinical laboratories should take part in external quality assessment (EQA) programs
to evaluate the bias of their method in comparison to other BNP methods. Finally, the authors
believe that the development of more specific methods for the active peptide, BNP1–32, should
reduce the systematic differences between methods and result in better harmonization of
results