Expression of β‐galactosidase multiple forms during barley (Hordeum vulgare) seed germination. Separation and characterization of enzyme isoforms

β‐Galactosidase (EC 3.2.1.23) activity in barley (Hordeum vulgare) seedlings increases moderately during the first stages of germination. The level of activity in the whole seedling is the result of increasing activity of β‐galactosidase in the roots and shoots and of declining enzyme activity in the grain. β‐Galactosidase was purified during different developmental stages and from various parts of the barley seedling using affinity chromatography and was resolved into multiple forms by isoelectric focusing on polyacrylamide gels. The expression of the isoforms was shown to be under temporal and tissue‐specific control. Four sets of isozymes were separated by DEAE‐cellulose chromatography and were shown to be functionally similar. β‐Galactosidase isoforms also exhibit size microheterogeneity, the more acidic entities having higher molecular masses. The differences in molecular weight are mainly restricted to the size of the small subunit. Multiplicity can not be attributed to glycosylation, since treatment of the enzyme preparation with N‐ or O‐glycanase did not alter the isoelectric points or the molecular weights of the isoforms.