Further studies on the reactions of disulphides with sodium sulphite.

although the prior formation of an unstable intermediate is not excluded. 4. The poor conversion ofesters ofD-galacturonic acid into compounds ofL-galactonic acid appears to be due mainly to the reversible inhibition of the enzyme during the course of the reaction, and to a lesser extent to the instability of the galactonic acid derivative formed. The substance responsible for the inhibition ofthe enzyme has not been identified. 5. The low affinity of the enzyme for methyl D-galacturonate (Ki, 10-2M) suggests that this is not the naturally occurring substrate. The work described in this paper was carried out as part of the programme of the Food Investigation Organization of the Department of Scientific and Industrial Research.