Wheat starch contains two classes of associated proteins: proteins which are embedded within the granule and loosely associated surface proteins. The characterisation of the major proteins that are embedded in the granule are described. Gel electrophoresis on the basis of size resolved these proteins into five bands of molecular weights 60, 75, 85, 100 and 105 kDa. These polypeptides were demonstrated to be within the granule by their resistance to proteinase K digestion when granules were ungelatinised. The N-terminal sequences of these polypeptides are reported. The most prominent polypeptide is the 60 kDa granule-bound starch synthase. The N-terminal sequence obtained from the 75 kDa polypeptide shows homology to rice soluble starch synthase. The 85 kDa band was resolved into at least two types of polypeptides, one of which reacted with polyclonal antiserum to the maize branching enzyme IIb. The 100 and 105 kDa polypeptides were located only in the granule and are related, on the basis of N-terminal sequence similarity and cross-reactivity to monoclonal antibodies. SDS-PAGE and monoclonal antibody cross-reactivity experiments suggest that the 100 and 105 kDa polypeptides are absent from starch granules from all other species examined, including other cereals. It is speculated that all the major granule proteins are involved in starch biosynthesis.

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Two groups off hordein-reactive antibodies (cross-reactive in barley with B/C monomers or subunits from the B/D-hordein aggregates) were used for the analysis of malt, wort and beer. A number of additional lower molecular weight hordein-derived polypeptides were present in water extracts of malts and worts, and protease inhibitors or higher mash-in temperature had a stabilising effect on certain hordein-derived polypeptides.The solubilisation profiles of hordein polypeptides monitored by specific immunological methods were clearly different from total wort polypeptides monitored by the Bradford method. There were also differences between the profiles for the two groups of hordein-derived polypeptides with the solubilisation of polypeptides recognised by antibody with specificity for the subunits from the B/D aggregates being especially temperature dependent.Beer samples mainly contained hordein-derived polypeptides of lower molecular weight than barley hordeins with polypeptides in the B and C molecular weight regions being lost during the brewing process. Beer polypeptides (Mr > 50,000) were recognised by antibodies cross-reactive with the subunits from the B/D aggregates in barley. A number of lower molecular weight polypeptides (Mr < 30,000) were recognised by antibodies with specificity for B and C hordeins; a subset of the latter antibody group bound to a specific Mr 23,000 beer polypeptide.