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Soluble enzymes in human dental plaque material were shown to synthetise a polysaccharide material when incubated with sucrose. The polysaccharide mixture was fractionated by gel chromatography and the major fraction (Mw congruent to 95,000) was characterised as a mixture of a alpha-(1 leads to 6)-linked glucan with branches linked alpha-(1 leads to 3) to the main chain and a beta-(2 leads to 6)-linked fructan with branches in the 1-position of the chain residues.

Dental plaque material, collected from five subjects, was pooled, homogenised and sonicated. The cell-free extracts and the remaining plaque suspension were incubated with sucrose. Approximately 14 per cent of the total "sucrase" activity was found in the cell-free extracts after homogenisation, 46 per cent in the cell-free extracts after sonication and 40 per cent in the remaining plaque suspension containing cell-fractions, respectively. Using gel chromatography of pooled plaque extracs from 10 subjects, active fractions were incubated with sucrose. The reaction products were isolated and characterised. The results indicate the presence of at least three groups of sucrose-splitting enzymes: dextransucrase, levansucrase and invertase.