Determination of purification ratio of Lake Maninjau in epilimnion zone

This study aims to determine the purification ratio (reaeration and deoxygenation ratio) in the epilimnion layer of Lake Maninjau. The parameters studied were BOD, COD, and environmental parameters such as temperature, pH, DO, wind speed and water velocity. Sampling was taken at three sampling station at east- and west side of the lake at 0, 2, 4, 6 m depth, and at 10 m depth of the center of the lake in the rain and not rain condition. The water quality of Lake Maninjau showed that the organics parameters had exceeded the quality standard. The organic substances measured as BOD ranged in average 12 mg/L and COD ranged in average 193 mg/L in rain conditions, whereas under dry conditions the BOD were higher i.e. in range of 22 mg/L and COD 218 mg/L. The deoxygenation rate (K1) during rain and dry were ranged in 0.047-0.371/day and 0.038-0.967/day respectively, whereas the reaeration rate (K2) of those were in the range of 0.117-0.647/day and 0.161-0.691/day respectively. The overall value of the purification ratio (K2/K1) of Lake Maninjau was in the range of 1.282-5.048 in rain condition and 1.107-7.230 in dry condition. It indicated, that Lake Maninjau in the epilimnion zone still has self-purification ability to assimilate the organic pollutants.

A new protease in hog thyroid lysosomes

A leupeptin-sensitive new protease was partially purified from hog thyroid lysosomes. The purification procedure included solubilization by hypotonic treatment of lysosomes, and Sephacryl S-300 and Sephadex G-100 gel chromatography, and the purification ratio was 10-fold from lysosomes. The pH optimum of the protease activity was around 5.5 and its molecular weight was estimated to be 22 000 by gel filtration. 2-Mercaptoethanol activated the hydrolysis of protein substrates and its effect was most pronounced in the case of thyroglobulin as substrate. Among the inhibitors used, leupeptin, antipain, toluenesulfonyl-lysine chloromethyl ketone and, to a lesser degree, chymostatin and toluenesulfonyl-phenylalanine chloromethyl ketone effectively inhibited the hydrolysis of casein by the enzyme at pH 5.5, whereas pepstatin did not inhibit the activity significantly. The enzyme activity was also inhibited by sulfhydryl inhibitors such as iodoacetamide, p-chloromercuribenzoate, and N-ethylmaleimide. The release of iodoamino acids from thyroglobulin by the enzyme was inhibited in the same manner by the inhibitors used in the hydrolysis of casein. The physiological role of the new protease is discussed in comparison with cathepsin B and L found in liver lysosomes.