Peroxidase Isozymes in Mature Barley Kernels

Polyphenolic Substrates of Cationic and Neutral/Anionic Peroxidases From Barley and Malt Using a Chronometric Method for the Determination of Pod Activity

“…Moreover, POD isoforms of most relevance in brewhouse reaction and contributing to the majority of POD-mediated oxidation will be those which will remain active into kiln-dried malt. We have already observed that basic and neutralJanionic POD fractions in solution exhibited different resistance to heat denaturation after exposure to temperatures applied during the kilning process (from 55 to 80C, unpublished work) as it has been shown with barley crude extracts (Laberge et al 1973) or with partially purified malt isoenzymes when heated at 35 and 55C . Therefore, we can assume that among oxidoreductases from malt which potentially have a role to play in oxidative reactions during malting and mashing, thermostable POD fractions will be of much relevance since activities of lipoxygenase, polyphenoloxidase and catalase partially or totally decline during the various stages of the beer production (Bamforth et al , 1993Clarkson et al 1991Clarkson et al , 1992Billaud et al 1997).…”

“…Often, POD activity originating from barley and malt has been assayed on various phenolics including guaiacol, o-dianisidine, pyrogallol, 3-amino-9-ethyl carbazole, 2,2'-azinodi-3-ethyl-benzothiazoline sulphonate or 4-methyl-a-naphthol (Laberge et al 1973;Laberge and Kruger 1976;Bamforth et al 1991;Cochrane 1994;Antrobus et al 1997) which are not present in barley. Thus, apart studies of Rasmussen et al, (1995) and Cochrane (1994), little is known about the enzymatic degradation of endogenous phenolics by POD from barley and malt.…”

Four major basic proteins of barley grain. Purification and partial characterization

“…During IEF in the high-pH range, precautions were taken to use COj-free solutions, and the pl-calculations were based on reference proteins (Delincee and Radola 1978). Peroxidase activity was detected with guaiacol or o-dianisidine as hydrogen donor (LaBerge et al 1973).…”

COMPARISON OF PEROXIDASES FROM BARLEY KERNEL (Hordeum vulgare L.) AND WHEAT GERM (Triticum aestivum L.): ISOLATION AND PRELIMINARY CHARACTERIZATION

“…In cereal crops such as barley and wheat seeds, distribution and nature of POD largely vary during growth and maturation of kernel and the pattern of enzyme development also depends on the cultivar (Laberge et al 1973; Kruger and Laberge 1974 a,b;Singh and Singh 1974; Laberge and Kruger 1976;Nadudvari-Markus et al 1984;Cochrane 1994). In cereals and within a given species, peroxidases seem to occur in a wide range of isoenzyme forms with p l values ranging from ca.…”

“…Depending on the pI value, they have been described as basic (cationic), neutral and acidic (anionic) and they can be separated and detected by electrophoretic and ion-exchange chromatographic (IEC) techniques. Up to fourteen cationic and/or anionic isoforms were detected from immature or malted grain of barley (Laberge et al 1973; Laberge and Kruger 1976;Clarkson et al 1991Clarkson et al , 1992 and tissues (Hejgaard et al 199 Kerby and Somerville 1992), in immature and germinated wheat (Honold and Stahmann 1968; Kobrehel et al 1972;Laberge et al 1973; Kruger and Laberge 1974a,b;Jeanjean et al 1975;Ion et al 1995), or in wheat germ (Shin and Nakamura 1961;Sequi et al 1968; Zmrhal and Machackova 1978;Converso and Fernandez 1995). Nevertheless, identification, biochemical characterization and comparison of isoenzymes are dificult owing to the great number of hydrogen donors used as substrates to detect POD activity (Laberge et al 1973; Converso andFernandez 1984, 1987; Thomasson et al 1995).…”