Subunit structure of karatasin, the proteinase isolated from Bromelia plumieri (karatas).
Close to 15% of the karatasin proteinase activity in the fruit juice of Bromelia plumieri (karatas) is present outside dialysis Visking tubing in 7 days in 0.2 M acetate buffer (pH) 3.5 or 6.5) containing phenyl mercuric acetate. The small proteinase(s), distinct from the 85% activity in juice due to nondialysable karatasin with a reported Mr of 24,868, separates across Spectrapore (13 kDa) membranes but not across Spectrapore with 3.5 kDa average pore diameter. The dialyzed proteinase is named karatasin-D (K-D). Purified non-Dialysable karatasin can be dissociated to what seems to be K-D by incubation in a buffer solution, containing SDS and 2-mercaptoethanol with phenyl mercuric acetate, in dialysis experiments for 8 days at room temperature using Spectrapore 13 kDa tubing. Thus, native karatasin in B. plumieri fruit juice seem to be the result of association of 2 small molecular mass K-D subunits, linked together by disulfide bonds and electrostatic forces, in equilibrium with small amounts of free K-D molecules. The amino acid composition and partial sequence of karatasin up to the 14th position from the amino terminus have discrete analogies with papain and with stem bromelain.
Montes
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Laboratorio de Bioquímica, Centro de Graduados, Instituto Tecnológico de Oaxaca, México.
Amador
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Cuevas
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Cordoba
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D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases; D003956:Dialysis; D010450:Endopeptidases / Q000302:isolation & purification* / Q000494:pharmacology; D005779:Immunodiffusion; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010944:Plants; D011480:Protease Inhibitors / Q000302:isolation & purification*
D046911:Macromolecular Substances; D011480:Protease Inhibitors; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C064907:karatasin