Subunit interactions in tyrosinase from frog epidermis in immobilized enzyme systems

Iborra, J. L.; Ferragut, José A.; Lozano, J A

doi:10.1042/bj1970581

Cited by 13 publications

(3 citation statements)

References 44 publications

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“…In turn, particulate tyrosinase would be in equilibrium between a micellar (with Brij 35) and a free form. An association-dissociation equilibrium has been described for tyrosinases from other sources (Vanneste & Zuberbuhler, 1974;Iborra et al, 1981), and an h.p.l.c. study was performed to clarify the significance of the different melanoma tyrosinases obtained so far.…”

Section: Mr Determinationmentioning

confidence: 99%

Aggregation equilibria of tyrosinase of Harding-Passey mouse melanoma

García-Borrón¹,

Solano²,

Iborra³

et al. 1985

Biochemical Journal

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The purification of two isoenzymes of tyrosinase has been carried out in Harding-Passey mouse melanoma. One is found in the cytosol and the other one bound to melanosomes. Both migrate as single bands on sodium dodecyl sulphate/polyacrylamide gels, having an apparent Mr of 58 000. Solubilized particulate tyrosinase showed an aggregation equilibrium involving a monomer, tetramer, octamer and a high-Mr micellar form with Brij 35, the solubilizing agent. H.p.l.c. studies indicated a interconversion between those species, the monomer contribution increasing with the sample dilution. The tetramer and the octamer probably represent the predominant forms in vivo. Soluble tyrosinase showed a simpler aggregation equilibrium, involving two forms, monomer and tetramer, with the same interconversion pattern. Fluorescence studies suggested that tryptophan residues were exposed to the aqueous environment when tyrosinase was dissociated by dilution. Tyrosinase shows a tendency to aggregate, at low protein concentration, and a resistance to dissociation by urea or SDS so remarkable that gel-permeation chromatography in 4M-urea does not affect the equilibrium, and the band obtained on SDS/polyacrylamide-gel electrophoresis is a dimer.

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Section: Mr Determinationmentioning

confidence: 99%

Aggregation equilibria of tyrosinase of Harding-Passey mouse melanoma

García-Borrón¹,

Solano²,

Iborra³

et al. 1985

Biochemical Journal

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“…Frog epidermis pro-tyrosinase was extracted and purified by the procedure of Lozano et al (1975), with two additional steps, involving CM-Sephadex and phenyl-Sepharose chromatography, as described by Iborra et al (1981). Epidermis was separated from dermis after incubation with a 2M-NaBr solution for 24h at 0-40C.…”

Section: Enzyme Preparationmentioning

confidence: 99%

The process for the activation of frog epidermis pro-tyrosinase

Peñafiel¹,

Galindo²,

Pedreño³

et al. 1982

Biochemical Journal

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1. Purified pro-tyrosinase from epidermis of the frog Rana esculenta ridibunda can be activated in vitro by several proteinases (trypsin, alpha-chymotrypsin, Pronase) and by light. 2. Both pro-tyrosinase and tyrosinase are composed of a single type of subunit having pI 7.2 and approximate molecular weights 68000 and 62000 respectively. A peptide of low molecular weight is released as a consequence of the proteolytic activation. Pro-tyrosinase and tyrosinase have different quaternary structures, the proenzyme being a dimer of Mr approx. 115000 and the enzyme a tetramer of Mr approx. 210 000. 3. The activation process was affected by several agents (L-3,4-dihydroxyphenylalanine, urea, formamide) that prevented, partially or totally, the activation of pro-tyrosinase. 4. The activation of pro-tyrosinase seems to be the result of a cleavage of the polypeptide chain that determines changes in tertiary or quaternary structure.

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“…In fact, the conformational unfolding caused by the trypsin treatment of protyrosinase (Iborra et al 1978;Lozano et al 1975) can also be partly induced by,. In fact, the conformational unfolding caused by the trypsin treatment of protyrosinase (Iborra et al 1978;Lozano et al 1975) can also be partly induced by,.…”

Section: Immobilization Yieldsmentioning

confidence: 99%