Detection of arylsulfatase A activity after electrophoresis in polyacrylamide gels: problems and solutions

Simultaneous, two-color fluorescence detection of total protein profiles and beta-glucuronidase activity in polyacrylamide gel

A dichromatic method for measuring the specific activity of beta-glucuronidase from complex cell homogenates or partially purified protein fractions is presented. Dual fluorescence is achieved by using the green emitting fluorogenic substrate ELF 97 beta-D-glucuronide to detect beta-glucuronidase activity, followed by the red emitting SYPRO Ruby protein gel stain or SYPRO Ruby IEF gel stain to detect the remaining proteins in the electrophoretic profile. Both ELF 97 alcohol, the highly fluorescent hydrolytic product generated from the enzyme substrate, and the SYPRO Ruby total protein stains are maximally excited by ultraviolet illumination. ELF 97 alcohol emits maximally at 525 nm while the SYPRO Ruby dyes emit maximally at 610 nm. Since ELF 97 beta-glucuronide is a precipitating substrate, it allows precise localization of beta-glucuronidase activity with minimal band diffusion. The staining method is simple and direct, without the requirement for ancillary coupling reactions. Dichromatic protein detection is demonstrated after sodium dodecyl sulfate(SDS)-polyacrylamide gel electrophoresis, carrier ampholyte-mediated isoelectric focusing or two-dimensional gel electrophoresis.

Pseudo arylsulfatase-A deficiency in healthy individuals: genetic and biochemical relationship to metachromatic leukodystrophy

Metachromatic leukodystrophy is a hereditary neurodegenerative disorder in man associated with deficient arylsulfatase-A activity (aryl-sulfate sulfohydrolase, EC 3.1.6.1). The same enzyme deficiency has been noted in clinically normal individuals, a condition known as pseudo arylsulfatase-A deficiency. With a nonselective method, somatic cell hybrids were obtained from cultured fibroblasts of these two types of individuals; the hybrids showed no restoration of arylsulfatase-A activity. Thus, metachromatic leukodystrophy and pseudo arylsulfatase-A deficiency are allelic conditions. Although these conditions cannot be distinguished by simple quantitative arylsulfatase-A activity assays, they can be differentiated with sucrose density gradient centrifugation, Cellogel electrophoresis, or isoelectric focusing in polyacrylamide gels. In each case, a small amount of activity with characteristics of arylsulfatase-A was found only from fibroblasts of pseudo arylsulfatase-A-deficient individuals and not from those of metachromatic leukodystrophy patients. This residual enzyme has the same pH optimum, heat stability, inhibitor sensitivity, and Km as the normal enzyme but slightly different isoelectric points. In conclusion, although pseudo arylsulfatase-A deficiency and metachromatic leukodystrophy have very different clinical outcomes, they are due to mutations of the same structural gene, coding for arylsulfatase-A. These two conditions can be differentiated now by simple electrophoretic analysis of the residual arylsulfatase-A activity.

Arylsulfatase A activity and electrophoretic banding patterns from isolated human blood fractions

Arylsulfatase A (ASA) activity was studied from five blood fractions, leukocytes plus platelets (LKPL), leukocytes (LK), neutrophils (N), lymphocytes (LYM), and platelets (PL). No significant difference was found among the mean ASA specific activity values for the fractions. Electrophoretic examination revealed four distinct activity bands for the LKPL and PL fractions, while the LK, N, and LYM fractions showed only a single, broad peak, which indicates that the four-band pattern is associated with enzyme obtained from platelets. The PL fraction gave a clearer, more distinct banding pattern than the other four fractions. This clearly resolved electrophoretic banding pattern of ASA from pure platelet preparations was demonstrated for variant human ASA as well. These findings may be significant to future work investigating the biochemical genetics of ASA.