Changing Kinetic Properties of Barley Alcohol Dehydrogenase during Hypoxic Conditions

The Finnish barley cultivar (Hordeum vulgare L, cv. Hankkija-673)was grown in solution culture for periods of one and two months.The one month old plants had seminal roots, whereas the twomonth old plants grew adventitious roots from the lower nodes.The roots were tested for ADH activity during aeration, during3 d of hypoxic treatment (brought about by passing nitrogenthrough the nutrient solution), and during a 4 d recovery period.The ADH activity, calculated on a protein basis, rose about4-fold during the nitrogen treatment, the greatest increaseoccurring in the adventitious roots. Differences in the kineticproperties of ADH during the hypoxic period were also foundbetween seminal and adventitious roots. The K_m for acetaldehydechanged little in the seminal roots during the hypoxic treatment,but in the adventitious roots it decreased considerably. Thephysiological significance of these changes is discussed. Key words: Hordeum vulgare, alcohol dehydrogenase, hypoxia, enzyme kinetics