Molecular features determining different partitioning patterns of papain and bromelain

ROCHA, M. VICTORIA; NERLI, BIBIANA

INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013

0141-8130

The partitioning patterns of papain (PAP) and bromelain (BR), two well-known cysteine-proteases, in polyethyleneglycol/sodium citrate aqueous two-phase systems (ATPSs) were determined.Polyethyleneglycols of different molecular weight (600, 1000, 2000, 4600 and 8000) were assayed. Ther-modynamic characterization of partitioning process, spectroscopy measurements and computationalcalculations of protein surface properties were also carried out in order to explain their differential parti-tioning behavior. PAP was observed to be displaced to the salt-enriched phase in all the assayed systemswith partition coefficients (KpPAP) values between 0.2 and 0.9, while BR exhibited a high affinity forthe polymer phase in systems formed by PEGs of low molecular weight (600 and 1000) with partitioncoefficients (KpBR) values close to 3. KpBRvalues resulted higher than KpPAPin all the cases. This differencecould be assigned neither to the charge nor to the size of the partitioned biomolecules since PAP and BRpossess similar molecular weight (23,000) and isoelectric point (9.60). The presence of highly exposedtryptophans and positively charged residues (Lys, Arg and His) in BR molecule would be responsible fora charge transfer interaction between PEG and the protein and, therefore, the uneven distribution of BRin these systems.