Three phase partitioning leads to subtle structural changes in proteins

Efficient three phase partitioning of actinidin from kiwifruit (Actinidia deliciosa) and its characterization

Three phase partitioning (TPP) method was effectively utilized for the extraction and purification of milk clotting protease (actinidin) from the kiwifruit pulp. The different purification parameters of TPP such as ammonium sulfate saturation, ratio of the crude kiwifruit extract to tert-butanol, and the pH value of extract were optimized. The 40% (w/v) salt saturation having 1.0:0.75 (v/v) ratio of crude kiwifruit extract to tert-butanol at 6.0 pH value exhibited 3.14 purification fold along with 142.27% recovery, and the protease was concentrated exclusively at intermediate phase (IP). This fraction showed milk-clotting activity (MCA), but there was no such activity in lower aqueous phase (AP). The enzyme molecular weight was found to be 24 kDa from Tricine SDS-PAGE analysis. Recovered protease demonstrated greater stability at pH 7.0 and temperature 50 °C. The Vmax and Km values were 121.9 U/ml and 3.2 mg/ml respectively. Its cysteine nature was demonstrated by inhibition studies. This study highlighted that the TPP is an economic and effective method for extraction and purification of actinidin from kiwifruit, and it could be used as a vegetable coagulant for cheesemaking.

Characterization of polyphenol oxidase from fennel (Foeniculum vulgare Mill.) seeds as a promising source

Fennel seeds were recognized as a promising polyphenol oxidase (PPO) source upon investigating some edible green plants (carob, jujube, coriander, fennel, and licorice). The fennel PPO enzyme was purified by three-phase partitioning and biochemically characterized in detail for the first time. The purification fold and activity recovery values were determined as 20-fold and 120%, respectively. Its molecular weight was 27.8 kDa. The temperature for the selected substrates (catechol, 4-tert-butylcatechol, 4-methylcatechol, and pyrogallol) was 30 °C, while the optimum pH value varied from 5.0 to 7.0 depending on the substrate. The k_cat/Km values exhibited that the enzyme presented the best activity towards catechol among the substrates used. Sodium metabisulfite, ascorbic acid, benzoic acid, l-cysteine, thiourea, β-mercaptoethanol, and glutathione prominently inhibited PPO activity. A remarkable decrease in PPO activity was observed at elevated concentrations of organic solvents, but in cases of the solvents with polarity indexes ≥5.1, the residual activity maintained more than 75% of its original activity up to 10% (v/v). Consequently, the current study suggested that fennel seeds could be used in various industrial sectors to produce low-cost polyphenol oxidase enzymes with an agricultural origin.

Application of three-phase partitioning to the purification and characterization of polyphenol oxidase from antioxidant rosemary (Rosmarinus officinalis L.)

Polyphenol oxidase (PPO) has been purified from the rosemary plant (Rosmarinus officinalis L.) through three-phase partitioning (TPP) and has been biochemically characterized. The optimized TPP consisted of 50% (w/v) ammonium sulfate and equal volumes of crude extract and tert-butanol prepared at pH 6.5 and room temperature. Using this system, PPO was purified 14-fold, with 230% recovery of activity from the middle phase. The partitioned enzyme had a molecular mass of 53 kDa. The highest enzyme activity was detected at 30 °C and pH 7.0 against catechol. In substrate specificity tests, the enzyme displayed activity towards catechol, 4-methylcatechol, caffeic acid, hydroquinone, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), pyrogallol, syringaldezine, and 3,4-dihydroxy-L-phenylalanine but no activity towards L-tyrosine. The enzyme was inhibited by the common PPO inhibitors; salicylhydroxamic acid (SHAM), cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP), and the organic solvent dimethyl sulfoxide (DMSO). Enzyme activity increased in the presence of the organic solvents acetone, ethanol, and methanol.

Partial Purification and Characterization of Polyphenol Oxidase from the Wild Edible Mushroom Lepiota Procera Using Three-Phase Partitioning

Polyphenol oxidase (PPO) from the wild edible mushroom Lepiota procera is partially purified and biochemically characterized using three-phase partitioning (TPP), which is an easily applied and effective method. This method includes ammonium sulfate saturation at different concentrations, t-butanol addition (1:1; 1:5), and adjustment of pH. Optimum purification parameters with 20% ammonium sulfate saturation and 1:1 t-butanol conditions led to the highest activity at bottom phase with 8.4 fold purification. Sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the molecular weight of the purified enzyme to be 35 kDa. The partially purified PPO presented a high level of activity with L-DOPA (Michaelis-Menten constant, Km – 0.12 mM), followed by caffeic acid (0.27 mM) and 4-methylcatechol (0.46 mM) and it is classified as a catecholase type of PPO. The enzyme had peak activity at a temperature of 40 °C and a pH value of 7.0. These results demonstrate a new enzyme source and easy purification method, useful for various industrial applications.

Obtaining a high activity subtilisin preparation by controlled thermal stress in n-octane

The use of enzymes in organic solvents has considerably widened their repertoire of applications. Such low water containing media also offer the possibility of carrying out enzymatic reactions at higher temperatures and enhancing reaction yields. The utility of such preparations is limited by the damage caused to the protein structure during freeze-drying. This work investigates the result of exposing the proteolytic enzyme subtilisin to high temperature in low water containing n-octane on its activity in aqueous and non-aqueous media. Exposing subtilisin at 90 °C for 5 h led to 18-fold improvement in its transesterification activity even at the normal assay temperature (37 °C) when compared with the untreated enzyme. The use of n-octane as the reaction medium was important as it helped to retain the three-dimensional architecture of the enzyme and should be considered while designing strategies for obtaining high activity preparations of other enzymes. Structural analysis using differential scanning fluorimetry showed that the enzyme lost its structure after heating in aqueous medium but retained it when heated in organic solvent. The simplicity and general applicability of the strategy should make it useful for obtaining highly active preparations of other enzymes as well.

Three phase partitioning and spectroscopic characterization of bioactive constituent from halophilic Bacillus subtilis EMB M15

In the present study, a halophilic Bacillus subtilis subsp. spizizenii (NCBI GenBank accession number KX109607) was isolated from the Sambhar Salt Lake, Rajasthan India. This organism exhibited significance antibacterial and antifungal activity against Proteus vulgaris, Bacillus subtilis, Aspergillus niger, Rhizopus oligosporus and Penicillium chrysogenum respectively. The bioactive constituent responsible for it was extracted by three phase partitioning and purified by column chromatography. The purified compound was further characterized by FTIR-ATR, NMR and Mass spectrometry. The mass spectra show a molecular ion of m/z 301.14. The compound has very high antimicrobial activity showing 35mm zone of inhibition against Bacillus subtilis.

Three phase partitioning, a scalable method for the purification and recovery of cucumisin, a milk-clotting enzyme, from the juice of Cucumis melo var. reticulatus

Cucumisin [EC 3.4.21.25] was first purified from Cucumis melo var. reticulatus juice by three-phase partitioning (TPP). Optimum purification parameters of the TPP system were determined as 60% ammonium sulfate saturation with 1.0:1.25 ratio of crude extract: t-butanol at pH and temperature of 8.0 and 20°C, respectively. Cucumisin was purified with 4.61 purification fold and 156% activity recovery. The molecular weight of the recovered cucumisin was determined as 68.4kDa and its isoelectric point is 8.7. Optimum pH and temperature of cucumisin were pH 9.0 and 60-70°C, respectively. The protease was very stable at 20-70°C and a pH range of 2.0-12.0. Km and Vmax constants were 2.24±0.22mgmL^-1 and 1048±25μ Mmin^-1, respectively. The enzyme was stable against numerous metal ions and its activity was highly enhanced by Ca²⁺, Mg²⁺, and Mn⁺². Cucumisin activity was 2.35-folds increased in the presence of 5mM of CaCl₂. It was inactivated by Co²⁺, Cd²⁺, Zn²⁺ and Fe²⁺ and dramatically by PMSF. Cucumisin milk-clotting activity was highly stable when stored under freezing (-20°C) compared at 4°C and 25°C. Finally, TPP revealed to be a useful strategy to concentrate and purify cucumisin for its use as a milk-clotting enzyme for cheese-making.

Three phase partitioning of zingibain, a milk-clotting enzyme from Zingiber officinale Roscoe rhizomes

The present work describes for the first time an elegant non-chromatographic method, the three phase partitioning for the purification and recovery of zingibain, a milk-clotting enzyme, from Zingiber officinale rhizomes. Factors affecting partitioning efficiency such as (NH4)2SO4 saturation, crude extract to t-butanol ratio and pH on zingibain partitioning were investigated. Optimal purification parameters were 50% (NH4)2SO4 saturation with 1.0:1.0 ratio of crude extract:t-butanol at pH 7.0, which gave 14.91 purification fold with 215% recovery of zingibain. The enzyme was found to be exclusively partitioned in the aqueous phase. The enzyme showed a prominent single band on SDS-PAGE. It is a monomeric protein of 33.8 kDa and its isoelectric point is 4.38. The enzyme exhibited maximal proteolytic activity at a temperature of 60 °C and pH 7.0. It was found to be stable at 40-65 °C during 2 h. The enzyme was found to be highly stable against numerous metal ions and its activity was enhanced by Ca(2+), K(+) and Na(+). It was completely inhibited by heavy metal ions such as Cu(2+) and Hg(2+) and partially by Cd(+). Zingibain milk-clotting activity (MCA) was found to be highly stable when stored under freezing (-20 °C) for 30 days compared at 4 °C.