Degradation of thymic humoral factor γ2 by human plasma: involvement of angiotensin converting enzyme

Comparative in vitro degradation of the human hemorphin LVV‐H7 in mammalian plasma analysed by capillary zone electrophoresis and mass spectrometry

“…The C-terminal truncation by the two last residues R 40 F 41 was caused by the Zn 2+ -dependent carboxypeptidase angiotensin-converting enzyme . ACE occurs in plasma membranes and in soluble plasma forms [46], and is known to cleave LVV-H7 at the herein detected sites [14][15][16]. Furthermore, LVV-H7 incubations in buffered ACE solution proved this conclusion experimentally (results not shown).…”

“…Plasma used for the studies described above was spiked with EDTA (1.6 mg/ml blood) while blood taking to prevent whole blood from aggregation. In addition, EDTA acts as a chelator of bivalent metal cations such as Zn 2+ , Mg 2+ and Ca 2+ known for their essential role for the activity of metalloproteinases [14,46]. To investigate the degradation profile of LVV-H7 in plasma in the absence of EDTA, citrate and heparin plasma also typical for clinical samples were tested.…”

Degradation of thymic humoral factor γ2 in human, rat and mouse blood: An experimental and theoretical study

“…Comparison with the behaviour in whole blood, reported here, shows a more rapid degradation with a half-life of less than 4 min, which is over three times lower than the value obtained in plasma [7]. Metabolism involved the rapid transient formation of Glu-Asp-Gly-Pro-Lys-Phe-Leu (2-8) followed by a slower formation of Asp-Gly-Pro-Lys-Phe-Leu (3-8) and 2-6 with small increases in 4-8 and 1-6.…”

“…As might be expected from the peptidases present in whole blood, the degradation of THF in human blood showed a more diverse pattern of products than that reported for plasma by Bramucci et al [7]. The differences are summarized in Fig.…”

“…Earlier work had shown the therapeutic value of the peptide to be limited by its relatively rapid metabolism in the blood. The half-life of THF in human plasma was reported to be about 12 min [7] and preliminary studies suggested that metabolism was faster in whole blood [8]. This led to the synthesis of analogues with greater stability [9], a process that could be aided by the identification of sites that are susceptible to degradative enzymes in blood.…”