Chemische Modifizierung von Proteinen. 8. Mitt. Beeinflussung physikochemischer und funktioneller Eigenschaften von Proteinen aus Ackerbohnen durch Succinylierung

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Recent data on the structure and chemical modification of the two main storage proteins of rapeseed, the high-molecular mass 12 S globulin and the low-molecular mass 2 S protein (napin) are summarized and compared with those of related seed proteins. The 12 S globulin is built up of six subunits forming a quaternary structure which can be approximated by the model of a trigonal antiprism. The subunits, composed of a larger and a smaller polypeptide chain each, have a two-domain structure which is typical for all related plant proteins. These are characterized by a sedimentation coefficient of 11-13 S, a molecular mass of 300,000-360,000 g/mol and a high percentage of beta-sheet conformation. Increasing succinylation results in a step-by-step dissociation up to the subunits and to an unfolding of the latter at a critical level of modification amounting to 60-70%. These structural changes affect the functional properties remarkably. The napin fraction comprises a group of closely related and highly basic proteins with molecular masses of 12,000-14,000 g/mol, a high content of sulphur-containing amino acids and rich in helical conformation. They are built up of a larger and a smaller disulphide bridged polypeptide chain. Acylation does not abolish the secondary or tertiary structure which are stabilized by inter- and intrachain disulphide bonds. Acylation results, however, in a stabilization of the protein against heat-induced aggregation.

Section: Functional Implications Of 1 1 S Protein Succinylationmentioning

confidence: 96%

Structural studies on native and chemically modified storage proteins from rapeseed (Brassica napus L.) and related plant proteins

Schwenke

1990

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“…Chemical derivatization through acylation of amino acid residues with acetic and succinic anhydride has been used to improve functional properties of many plant proteins including wheat [11], soybean [4], leaf protein [12], peanut [13], sunflower [14], pea [15], cotton seed [16], winged bean [17], Faba bean [18][19][20], soy glycinin [21,22], rapeseed [23][24][25], and chick pea [26]. So far, no literature is available on acylation of mucuna beans.…”

Section: Introductionmentioning

confidence: 99%

Effect of acetylation and succinylation on solubility profile, water absorption capacity, oil absorption capacity and emulsifying properties of mucuna bean (Mucuna pruriens) protein concentrate

Lawal

Adebowale²

2004

Mucuna protein concentrate was acylated with succinic and acetic anhydride. The effects of acylation on solubility, water absorption capacity, oil absorption capacity and emulsifying properties were investigated. The pH-dependent solubility profile of unmodified mucuna protein concentrate (U-mpc) showed a decrease in solubility with decrease in pH and resolubilisation at pH values acidic to isoelectric pH (pH 4). Apart from pH 2, both acetylated mucuna protein concentrates (A-mpc) and succinylated mucuna protein concentrate (S-mpc) had improved solubility over the unmodified derivative. Acylation increased the water absorption capacity (WAC) at all levels of ionic strength (0.1-1.0 M). WAC of the protein samples increased with increase in ionic strength up to 0.2 M after which a decline occurred with increase in ionic strength from 0.4-1.0 M. When protein solutions were prepared in salts of various ions, increase in WAC followed the Hofmeister series in the order: NaSCN < NaClO4 < NaI < NaBr < NaCl < Na2SO. Acetylation improved the oil absorption capacity while the lipophilic tendency reduced the following succinylation. Emulsifying capacity increased with increase in concentration up to 2, 4 and 5% w/v for U-mpc, A-mpc and S-mpc, respectively, after which an increase in concentration reduced the emulsifying capacity. Both acetylation and succinylation significantly (P < 0.05) improved the emulsifying capacity at pH 4-10. Initial increase in ionic strength up to 0.4 M for U-mpc and 0.4 M for A-mpc and S-mpc increased the emulsion capacity progressively. Further increase in ionic strength reduced emulsion capacity (EC). Contrary to the effect of various salts on WAC, increase in EC generally follows the series Na2SO4 < NaCl < NaBr < NaI < NaClO4 < NaSCN. At all levels of ionic strength studied, S-mpc had a better emulsifying activity (EA) than both A-mpc and U-mpc. EA and emulsifying stability (ES) were pH-dependent. Maximum EA and ES were recorded at pH 10. ES of protein derivatives were higher than those of U-mpc in the range of pH 4-10 but lower at pH 2. Studies revealed that both A-mpc and S-mpc had better ES and EA than the unmodified derivative when protein solutions were prepared in salts of various anions.

“…The unfolding was detected by a sudden increase of the intrinsic viscosity and drastic changes of the UV and C D spectra. The present paper deals with the influence of different degrees of succinylation on viscometric and microcalorimetric data of a protein isolate from Viciufubu containing about 73 % legumin and about 23% vicilin [4].Fig . I shows the plot of intrinsic viscosity versus the degree of amino groups succinylation in the faba bean protein isolate.…”

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confidence: 99%

‘Continuous’ conformational change in succinylated faba bean protein isolates

Schwenke

Prahl

Danilenko

et al. 1990

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Succinylation causes a step-by-step dissociation of oligomeric 11 S storage proteins into subunits (1, 2). In previous papers it was shown that with the 11 S proteins from peanuts [l], sunflower seeds [2] and rapeseeds [3] a 'critical step' of.succinylation occurs at which the dissociation into monomeric subunits takes place and the unfolding of proteins begins. This 'critical step' has been found to correspond to adegree of 60-70 % succinylation in all ofthese proteins. The unfolding was detected by a sudden increase of the intrinsic viscosity and drastic changes of the UV and C D spectra. The present paper deals with the influence of different degrees of succinylation on viscometric and microcalorimetric data of a protein isolate from Viciufubu containing about 73 % legumin and about 23% vicilin [4].Fig . I shows the plot of intrinsic viscosity versus the degree of amino groups succinylation in the faba bean protein isolate. For comparison the previously published data on succinylated 11 S proteins from sunflower and rapeseed are shown, too. Contrary to latter groups the faba bean protein preparations revealed a continuous increase of the intrinsic viscosity with an increasing degree of succinylation. While the sunflower and rapeseed proteins showed an almost unchanged viscosity up to a degree ofabout 60 % succinylation, the viscosity of moderately (36-49 %) succinylated faba bean protein already reached viscosity values corresponding to those of partially unfolded proteins [5].When the apparent viscosity in concentrated (8 %) faba protein solutions was measured during a cyclic heatingcooling process, a viscosity minimum appeared at 65 "C, Under further heating the viscosity increased again [6]. This viscosity increase was assumed to be related to the structural unfolding of the proteins. At high degrees of succinylation where the unfolding already took place at room temperature the value of Atj was 0. As Table 1 shows, a continuous drop of Atj occurred with increasing succinylation pointing to conformational changes already at moderate degrees of modification. The measurements were performed at pH 8.0 -Ssrenson Phosphate/NaCl buffer (p = 0.5) and Tris HCl/ NaCl buffer (p = 0.5) using 1 % protein solutions and a VISCOMATIC (FICA, Switzerland) Type viscometer.