title: Chemical modification of lysine residues in Bacillus licheniformis alpha-amylase: conversion of an endo- to an exo-type enzyme.
abstract: The lysine residues of Bacillus licheniformis alpha-amylase (BLA) were chemically modified using citraconic anhydride or succinic anhydride. Modification caused fundamental changes in the enzymes specificity, as indicated by a dramatic increase in maltosidase and a reduction in amylase activity. These changes in substrate specificity were found to coincide with a change in the cleavage pattern of the substrates and with a conversion of the native endo- form of the enzyme to a modified exo- form. Progressive increases in the productions of rho-nitrophenol or glucose, when para nitrophenyl-maltoheptaoside or soluble starch, respectively, was used as substrate, were observed upon modification. The described changes were affected by the size of incorporated modified reagent: citraconic anhydride was more effective than succinic anhydride. Reasons for the observed changes are discussed and reasons for the effectivenesses of chemical modifications for tailoring enzyme specificities are suggested.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran. P. O. Box: 13145-1384, Tehran, Iran.
authors.forename: Azadeh Ebrahim
authors.initials: AE
authors.lastname: Habibi
authors.forename: Khosro
authors.initials: K
authors.lastname: Khajeh
authors.forename: Mohsen
authors.initials: M
authors.lastname: Nemat-Gorgani
mesh_terms: D000812:Anhydrides / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008239:Lysine / Q000737:chemistry*; D015394:Molecular Structure; D013379:Substrate Specificity; D000516:alpha-Amylases / Q000737:chemistry / Q000378:metabolism
chemical_list: D000812:Anhydrides; D001426:Bacterial Proteins; D000516:alpha-Amylases; C501919:alpha-amylase, Bacillus licheniformis; D005947:Glucose; D008239:Lysine