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.
Laboratorio de Bioquímica, Centro de Graduados, Instituto Tecnológico de Oaxaca, México.
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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