Immunochemical assay for deoxyribonuclease activity in body fluids.

We have developed two microtiter plate assays to quantify the deoxyribonuclease activity in biological fluids. Both assays are based on hydrolysis of biotinylated and fluorescein-labeled DNA substrates, with subsequent immunochemical detection of non-digested DNA. The assay based on hydrolysis of 974 bp PCR product labeled with biotinylated forward and fluorescein-labeled reverse primers is more sensitive (0.05 U/ml) and convenient for quantifying the DNase activity in biological fluids than the assay based on hydrolysis of double-labeled 20 bp oligonucleotide. The DNase activity in urine and blood plasma of healthy donors was measured using the PCR product-based assay. Urine samples revealed greater activity, 1.49+/-1.41 U/ml; blood plasma DNase I-like activity was 0.36+/-0.20 U/ml. DNase II-like activity was not detected in the plasma samples. The data obtained confirm that DNase I-like enzymes are responsible for the majority of deoxyribonuclease activity in blood plasma.

Human urine deoxyribonuclease II (DNase II) isoenzymes: a novel immunoaffinity purification, biochemical multiplicity, genetic heterogeneity and broad distribution among tissues and body fluids.

Deoxyribonuclease II (DNase II) was purified from the urine of a 48-year-old male (a single individual) using a column chromatography series, including concanavalin A-agarose and an immunoaffinity column utilizing anti-human spleen DNase II antibody, and was then characterized. Based on the catalytic properties of the purified enzyme, we have devised a technique of isoelectric focusing by thin-layer polyacrylamide gel electrophoresis (IEF-PAGE) combined with a specific zymogram method, for investigating the possible molecular heterogeneity of human DNase II. DNase II in urine as well as the purified form was found to exist in multiple forms with different pI values separable by IEF-PAGE within a pH range of 5-7. Since sialidase treatment of the urine sample induced simplification of the isoenzyme patterns with diminishment of anodal bands, it was clear that the multiplicity of the enzyme was in part due to differences in the sialic acid content. On screening of DNase II isoenzyme patterns in urine samples from more than 200 Japanese individuals, only the common isoenzyme pattern was observed and no electrophoretic variations were detected. However, genetic studies of urinary enzyme activity and comparative studies on the activity in urine, semen and leukocytes from the same individuals suggest that the enzyme activity level of DNase II may be under genetic control. The enzyme was widely distributed in human tissues and showed high activities in secretory body fluids such as breast milk, saliva, semen and urine, and leukocyte lysates.

Genetic polymorphism of human deoxyribonuclease II (DNase II): low activity levels in urine and leukocytes are due to an autosomal recessive allele.

The objectives of this study were to elucidate the genetic basis of human deoxyribonuclease II (DNase II) and to evaluate its usefulness as a genetic and/or diagnostic marker. We have devised a novel, specific and highly sensitive assay method for the urinary and leukocytic enzymes (Yasuda et al. 1991). The distribution of the activities of both enzymes displayed clear-cut bimodality and the Japanese study population could be classified into two distinct types, namely low-activity (DNASE2 L) and high-activity (DNASE2 H), which indicates the existence of a genetic polymorphism in the activity levels of urinary and leukocytic DNase IIs. Close correlations between the leukocytic and urinary enzyme activity levels from the same individuals were observed and the types in the leukocyte samples agreed with the types found in the corresponding urine samples. In a population study of 528 unrelated Japanese individuals, the gene frequencies of the low activity (DNASE2*L) and the high activity (DNASE2*H) alleles were calculated to be 0.632 and 0.368, respectively. The sex and age of individuals did not affect the distribution of DNase II activity levels. The family study results were compatible with the model that the low activity type is due to an autosomal recessive gene, which indicates that DNASE2 L represents homozygosity for DNASE2*L and DNASE2 H corresponds to homozygosity for DNASE2*H and heterozygosity for DNASE2*L and DNASE2*H.

Human urine DNase I: immunological identity with human pancreatic DNase I, and enzymic and proteochemical properties of the enzyme.

DNase I in human urine was purified to an electrophoretically homogeneous state by column chromatographies on DEAE-lignocellulose, hydroxyapatite, DEAE-cellulose, Sephadex G-75 and elastin-celite. The purified enzyme was immunologically identical with human pancreatic DNase I, but not with bovine pancreatic DNase I. The molecular weight and isoelectric point of the enzyme were estimated to be 4.1 X 10(4) and 3.6, respectively. The amino acid analysis revealed that 1 mol of the enzyme contained 8 mol of half-cystine. The N-terminal amino acid was identified as leucine by the dansyl chloride method. The enzyme was active in the presence of Mg2+, Co2+, or Mn2+, The optimum pH was around 6.5. The enzyme was stable in the pH range from 5.0 to 9.0 and at temperatures lower than 45 degrees C. The rate of hydrolysis of native DNA by the enzyme was twice as fast as that observed with heat-denatured DNA. This enzyme exhaustively degraded about 20% of the phosphodiester bonds in native DNA. The enzyme also degraded poly(dA) and poly(dT), but hardly degraded poly(dG) and poly(dC).