o:31941 Interaction between alpha-2-macroglobulin and phycocyanobilin-structural and physiological implications Interakcija izmedju alfa-2-makroglobulina i fikocijanobilina-strukturne i fiziološke posledice en ABSTRACT In this study, the interaction between phycocyanobilin (PCB) 1, a bioactive chromophore of blue-green algae Spirulina's phycobiliproteins, and alpha-2-macroglobulin (α2M)2, a universal anti-proteinase, was investigated under simulated physiological conditions using spectroscopic techniques and α2M activity assay. Using spectrofluorimetric measurements, we found that α2M binds PCB with a moderate affinity, with a binding constant of 6.3×10 5 M−1 at 25°C. The binding of PCB to α2M does not cause any significant change in the secondary structure of the protein (circular dichroism measurements). Besides, PCB protects α2M from structural oxidative alterations under AAPH-induced free radical overproduction. Further, PCB binding effectively preserves α2M anti-proteinase activity. Since α2M is involved in controlling the action of enzymes during the inflammatory process, the protection that PCB expresses could indirectly influence the intensity and direction of body response to impaired homeostasis, especially under oxidative stress. phycocyanobilin, alpha-2-macroglobulin, 1552102 https://febs.onlinelibrary.wiley.com/doi/pdf/10.1002/2211-5463.13440 1552099 10.1002/2211-5463.13440 2023-12-05T13:09:37.511Z 44 yes 46 Miloš Šunderić University of Belgrade, Institute for the Application of Nuclear Energy INEP, Serbia doktor biohemijskih nauka 0000-0002-0940-9481 Milan R. Nikolić University of Belgrade, Faculty of Chemistry, Serbia person Olgica Nedić University of Belgrade, Institute for the Application of Nuclear Energy INEP, Serbia doktor biohemijskih nauka person 0000-0003-2042-0056 Simeon Minić University of Belgrade, Faculty of Chemistry, Serbia person Nikola Gligorijević University of Belgrade, Institute for the Application of Nuclear Energy INEP, Serbia person application/pdf 2738960 https://phaidrabg.bg.ac.rs/o:31941 no yes 18 70 92000004 11A29 11A2905 11A19 The Biochemistry Global Summit, 25th IUBMB Congress, 46th FEBS Congress, 15th PABMB Congress, Lisbon, Portugal Wiley 2022