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An investigation of human biological variation in urinary organic acids, including pyroglutamic acid along with 39 other compounds, was previously reported in which levels were determined for 8 weeks in healthy adult subjects. Here, unique, 4‐week‐long physiological trends for one of those compounds, pyroglutamic acid (PGA), are reported. When PGA levels for an individual rose above 40 μg/mg creatinine, 4‐week downward progressions occurred until levels reached values near 15 μg/mg creatinine and the pattern was reversed when levels for an individual were below that level in the early weeks of the study. The pattern was especially prominent among 8 of the 13 menstruating female subjects suggesting a possible association with metabolic stress of the menstrual cycle. However, it also appeared in 3 of the 8 male subjects where other sources of metabolic stress may be present. The menstrual association is consistent with estrogen‐mediated increase in oxidative stress. Since PGA is linked to glutathione turnover, the consistency of extreme values across all individuals displaying the pattern indicates that 15 and 40 μg/mg creatinine may represent limits that trigger shifts in sulfur amino acid metabolism. This is the first observation of approximate month‐long cyclic responses in a glutathione‐related urinary marker in humans.

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SynopsisOligopeptides containing glycine and one or two Galanyl or tglutamyl residues have been studied by circular dichroism (CD) and optical rotatory dispersion (ORD) in aqueous solution a t pH 1.0, pH 6.0, and pH 10.0 and in aqueous ethanol. Two glycyl residues are required to remove effects of a-carboxyl or amino titration on the optical activity of the internal alanyl or glutamyl residues. The CD spectra of the alanyl and protonated glutamyl residues are similar, having two regions of negative ellipticity with minima around 228 and 195 nm. The CD spectrum of the ionized glutamyl residue has an additional region of positive ellipticity around 215 nm resulting in a spectrum resembling that of poly-a-kglutamic acid (PGA) a t high pH. Another large positive band below 190 nm was observed for glyrglurglyz in water at pH 6 and 10 and for several peptides in aqueous ethanol. Residue ellipticities were approximately additive in every case except for peptides containing internal glutamyl residue at pH 6.0.