ENZYMATIC RELEASE OF AMINO-ACIDS FROM DIFFERENT HUMIC SUBSTANCES

Humic substances isolated from water, sediment, and soil were characte rized by applying elemental analysis, spectroscopic analysis, and gelc hromatographic molecular size distribution. In addition, the amounts a nd pattern of enzymatically released amino acids were determined. Depe nding on the origin of the humic substances, the percentage of release d amino acid nitrogen related to the total nitrogen was in the range o f 0.4 to 26.7%. The samples particularly differed in the content of le ucine und tyrosine. The total amount of released amino acids was compa red with the results obtained from the other characterization methods. This approach indicated that humic substances with a high content of hydrolysable amino acids had high N/C and O/C ratios and low molecular sizes. Beside this, the absorption of these substances in the UV and visible wavelength range was quite low, while the measured ratios of S AK (254)/SAK (436) showed high values. This work leads to the conclusi on that the extent of enzymatically releasable amino acids is not only dependant on the nitrogen content of humic substances. Other physical and chemical properties have to be considered for the understanding o f the results obtained by the described biochemical characterization m ethod.