Pyroglutamyl peptidase-II ("thyroliberinase") activity in human serum: influence of weight and thyroid status.

Abstract

The tripeptide hormone, TRH, is metabolized by three enzymes, the most specific of which is pyroglutamyl peptide hydrolase-II (also termed thyroliberinase), a metalloenzyme present in serum and brain. Because pyroglutamyl peptidase-II activity in rat serum is regulated by thyroid hormone levels, we tested the hypothesis that this activity is similarly altered in humans. We studied serum pyroglutamyl peptidase-II activity in 6 patients with hyperthyroidism, 18 patients with hypothyroidism, and 31 euthyroid, normal weight volunteers. Because TRH [or its metabolite cyclo(His-Pro)] is believed to be an important hormone regulating appetite and metabolism, we also evaluated pyroglutamyl peptidase-II activity in 27 euthyroid patients with obesity. Serum pyroglutamyl peptidase-II activity was elevated in patients with hypothyroidism (mean +/- SEM, 33.9 +/- 3.7 nmol/mL.h) compared to that in euthyroid, normal weight volunteers (24.5 +/- 2.8 nmol/mL.h; P < 0.05), but not that in patients with hyperthyroidism (28.3 +/- 4.1 nmol/mL.h; P = NS). Euthyroid obese patients had the highest pyroglutamyl peptidase-II activity (43.6 +/- 2.8 nmol/mL.h; P < 0.0001 vs. normal weight volunteers). Pyroglutamyl peptidase-II activity was positively correlated with body mass index (r2 = 0.30; P < 0.0001). After correction for body mass index, there were no difference in pyroglutamyl peptidase-II activity in hypothyroid, hyperthyroid, and euthyroid individuals. We conclude that serum pyroglutamyl peptidase-II activity is regulated by, or regulates, body weight.

• Authors: T C Friedman, J A Yanovski, V Jayasvasti, S Z Yanovski, R J Koenig, S Wilk
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 80 Issue 4 Pg. 1086-9 (Apr 1995) ISSN: 0021-972X [Print] United States
• PMID: 7714073 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Aminopeptidases
• pyroglutamyl-peptidase II
• Pyrrolidonecarboxylic Acid

Topics

• Adult
• Aminopeptidases (blood)
• Body Mass Index
• Body Weight
• Female
• Humans
• Hyperthyroidism (blood)
• Hypothyroidism (blood)
• Male
• Obesity (blood)
• Pyrrolidonecarboxylic Acid (analogs & derivatives)
• Reference Values