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  • Title: Dissociation and reassociation of immobilized porphobilinogen synthase: use of immobilized subunits for enzyme isolation.
    Author: Gurne D, Chen J, Shemin D.
    Journal: Proc Natl Acad Sci U S A; 1977 Apr; 74(4):1383-7. PubMed ID: 266180.
    Abstract:
    The dissociation and association of an immobilized preparation of the octameric enzyme porphobilinogen synthase [5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing), EC 4.2.1.24] is described. On treatment of the immobilized preparation with 4 M urea, four subunits per octamer are removed which can be reassociated into a soluble octameric enzyme. The tetrameric bound residual protein can also be reassembled into an octameric structure, with the same initial enzyme activity, by exposing the residual bound protein to a soluble pure enzyme preparation or to a crude liver extract in the presence of urea. The dissociation of the reconstituted bound enzyme releases subunits that again can be reassembled into a soluble octameric pure protein even when the crude liver preparation is used as the donor of the subunits. Thus, a pure enzyme can be isolated in a reassociation-dissociation cycle. The use of immobilized preparations of oligomeric proteins is considered for intra- and interspecies hybridization studies and for the ready preparation of purified enzyme preparations from different species and is suggested as a model for study of the formation of an oligomeric enzyme in the presence of other polypeptides.
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