title: Study on the interaction of β-carotene and astaxanthin with trypsin and pepsin by spectroscopic techniques.
abstract: β-Carotene and astaxanthin are two carotenoids with powerful antioxidant properties, but the binding mechanisms of β-carotene/astaxanthin to proteases remain unclear. In this study, the interaction of these two carotenoids with trypsin and pepsin was investigated using steady-state and time-resolved fluorescence measurements, synchronous fluorescence spectroscopy, UV-vis absorption spectroscopy and circular dichroism (CD) spectroscopy. The experimental results indicated that the quenching mechanisms of trypsin/pepsin by the two carotenoids are static processes. The binding constants of trypsin and pepsin with these two carotenoids are in the following order: astaxanthin-trypsin > astaxanthin-pepsin > β-carotene-trypsin > β-carotene-pepsin, respectively. Thermodynamic investigations revealed that the interaction between the two carotenoids and trypsin/pepsin is synergistically driven by enthalpy and entropy, and hydrophobic forces and electrostatic attraction have a significant role in the reactions. In addition, as shown by synchronous fluorescence spectroscopy, UV-vis absorption spectroscopy and CD, the two carotenoids may induce conformational and microenvironmental changes in trypsin/pepsin. The study provides an accurate and full basic data for clarifying the binding mechanisms of the two carotenoids with trypsin/pepsin and is helpful in understanding their effect on protein function and their biological activity in vivo.
authors.affiliation: Department of Chemistry, School of Basic Medicine, Xinxiang Medical University, Xinxiang, Henan, 453003, People's Republic of China.
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Li
authors.affiliation: The Clinical Skills Training Center, Xinxiang Medical University, Xinxiang, Henan, 453003, People's Republic of China.
authors.forename: Peihong
authors.initials: P
authors.lastname: Li
mesh_terms: D002942:Circular Dichroism; D010434:Pepsin A / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014357:Trypsin / Q000737:chemistry*; D024341:Xanthophylls / Q000737:chemistry; D019207:beta Carotene / Q000737:chemistry*
chemical_list: D024341:Xanthophylls; D019207:beta Carotene; C005948:astaxanthine; D014357:Trypsin; D010434:Pepsin A
keywords: astaxanthin; pepsin; spectroscopy; trypsin; β-carotene