title: Enzyme activity of α-chymotrypsin: Deactivation by gold nano-cluster and reactivation by glutathione.
abstract: Effect of gold nanoclusters (Au-NCs) on the circular dichroism (CD) spectra and enzymatic activity of α-chymotrypsin (ChT) (towards hydrolysis of a substrate, N-succinyl-l-phenylalanine p-nitroanilide) are studied. The CD spectra indicate that on binding to Au-NC, ChT is completely unfolded, resulting in nearly zero ellipticity. α-chymotrypsin (ChT) coated gold nano-clusters exhibit almost no enzymatic activity. Addition of glutathione (GSH) or oxidized glutathione (GSSG) restore the enzyme activity of α-chymotrypsin by 30-45%. ChT coated Au-NC exhibits two emission maxima-one at 480nm (corresponding to Au10) and one at 640nm (Au25). On addition of glutathione (GSH) or oxidized glutathione (GSSG) the emission peak at 640nm vanishes and only one peak at 480nm (Au10) remains. MALDI mass spectrometry studies suggest addition of glutathione (GSH) to α-chymotrypsin capped Au-NCs results in the formation of glutathione-capped Au-NCs and α-chymotrypsin is released from Au-NCs. CD spectroscopy indicates that the conformation of the released α-chymotrypsin is different from that of the native α-chymotrypsin.
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
authors.forename: Catherine
authors.initials: C
authors.lastname: Ghosh
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
authors.forename: Tridib
authors.initials: T
authors.lastname: Mondal
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India; Department of Chemistry, Indian Institute of Science Education & Research Bhopal, Bhopal Bypass Road, Bhauri, Bhopal 462 066, Madhya Pradesh, India. Electronic address: kankan.bhattacharyya@gmail.com.
authors.forename: Kankan
authors.initials: K
authors.lastname: Bhattacharyya
mesh_terms: D002918:Chymotrypsin / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D005978:Glutathione / Q000378:metabolism* / Q000494:pharmacology*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: C011358:Suphepa; D010649:Phenylalanine; D006046:Gold; D002918:Chymotrypsin; C117608:alpha-chymotrypsin; D005978:Glutathione
keywords: Chymotrypsin; Glutathione; Gold nano cluster; MALDI mass spectrometry