Enzyme polymorphism in rat-liver microsomes and plasma membranes. 2. An immunochemical comparison of enzyme-active antigens solubilized by detergents, papain or phospholipases

Tumour-associated antigens reacting with cytotoxic antibodies in serum of hepatoma-bearing rats

3M-KCl extracts of the hepatoma D23 contain antigens that inhibit the complement-dependent cytotoxicity for D23 hepatoma cells of serum from D23 tumour-bearing rats (D23 TBS). Inhibition was not due to a general anticomplementary activity of the extracts. Although a minor part (25%) of the protein of D23-KCl extract was insoluble in PBS, this part contained most of the inhibitory activity. Fractionation of the PBS-soluble material of the extract on Concanavalin A-Sepharose showed that the inhibitory activity did not bind to the lectin. Analysis of D23-KCl extracts on a Sepharose CL-4B column showed that the antigens involved in the cytotoxicity were heterogeneously distributed in the high-mol. wt region (greater than 200,000). Precipitation with 10% trichloroacetic acid (TCA) of D23 KCl extracts revealed that most of the antigenicity was insoluble in TCA. Heating of D23 KCl extracts at 100 degrees C did not affect the antigenicity. Enzyme treatment of D23 extra nuclear membranes (D23 ENP) revealed that the inhibitory activity was not sensitive to proteolytic digestion, while treatment with phospholipase A2, C or D abrogated partly the inhibitory activity. The lipid nature of the antigenicity was indicated by its solubility in organic solvents as chloroform or n-butanol.

Arylamidases of rat liver and chemically induced hepatomas. 1. Subcellular distribution of L-leucine. 2. Naphthylamidase-active antigens

The subcellular distribution of arylamidase-active antigens in rat liver and in two chemically induced hepatomas (D23 and D33) was investigated. Soluble antigens or detergent-solubilized membrane antigens from isolated subcellular fractions were tested in fused rocket immunoelectrophoresis against antisera prepared against each of the fractions. The arylamidase active antigens were identified by means of a zymogram technique using L-leucine 2-naphthylamide as substrate. Two arylamidase-active antigens were shown to be shared between plasma membranes, microsomes, lysosomal membranes and lysosomal content of the hepatocytes. One of these occurred predominantly in the plasma membranes (the plasma membrane arylamidase) while the other was preferentially found in the lysosomal content (the lysosomal content arylamidase). Also a third arylamidase-active antigen was identified and was shown to be restricted to the microsomes and the lysosomal membranes (the microsomal/lysosomal arylamidase). The rat liver plasma membrane arylamidase-active antigen was also present in plasma membrane, microsomal and cell-sap fractions of both the hepatomas. However, in the hepatomas this antigen occurred predominantly in the microsomal fraction. The plasma membrane arylamidase was the only arylamidase-active antigen found in the hepatoma D33 while the plasma membrane and microsomal fractions of hepatoma D23 also contained another antigen with this activity. Neither the lysosomal content arylamidase nor the microsomal/lysosomal arylamidase could be detected in any of the hepatoma fractions.

Comparison of human membrane-bound neutral arylamidases from small intestine, lung, kidney, liver and placenta

Human membrane-bound neutral arylamidases were solubilized from small intestinal mucosa, lung, kidney, liver and placenta with trypsin. These five membrane-bound neutral arylamidases were identified by polyacrylamide gel-disc electrophoresis. The heat sensitivity of each enzyme was in the order, liver and placenta greater than kidney greater than lung greater than small intestine. This order correlates with that of electrophoretic mobility, except for the placental membrane-bound neutral arylamidase. Five membrane-bound neutral arylamidases have the same molecular weight, 240 000, as estimated by Sephadex G-200 gel filtration. The five membrane-bound neutral arylamidase have very similar KM values (8.7 x 10(-5) M towards L-alanyl-beta-naphthylamide), optimal pH values, hydrolysis ratios towards L-alanyl-beta-naphthylamide and L-leucyl-beta-naphthylamide, and sensitivities of inhibition by chelators or amino acids. These results suggest that the multiple forms of membrane-bound neutral arylamidase found in five different human organs are organ-specific isoenzymes.

Arylamidases of rat liver and chemically induced hepatomas. II. Preparation and characterization of monospecific antisera against two distinct arylamidase-active antigens

Monospecific antisera were prepared against the most prominent arylamidase (alpha-aminoacyl-peptide hydrolase (microsomal), EC 3.4.11.2) active antigen in plasma membranes (the plasma membrane arylamidase) and lysomal content (the lysosomal content arylamidase), respectively. Plasma membrane extract and lysosomal content were allowed to react in crossed immunoelectrophoresis against their homologous antisera. The electrophoretic plates were washed extensively, dried and subsequently stained for arylamidase activity. The particular immunoprecipitates were thus identified and could be excised to be used for immunizations. The two resulting antisera precipitated the arylamidase used for immunization, but failed to be monospecific as they precipitated additional antigens. These antisera with restricted specificity against some plasma membrane and lysosomal content antigens, respectively, were used to produce immunoprecipitates intended for new attempts to prepare monospecific antisera by a second cycle of immunizations. A monospecific antiserum against the plasma membrane arylamidase was thus obtained, while a third cycle of immunizations was needed to get a monospecific anti-lysosomal content antiserum. The plasma membrane arylamidase showed ATPase activity also after precipitation with the monospecific antiserum, thus still retaining its characteristics as a multienzyme complex.

Localization of enzymes in specialized regions of the microsomal membrane

Microsomal vesicles were centrifuged through sucrose density gradients containing deoxycholate. With 0.15% detergent electron transport enzymes and phosphatases could be separated. Increasing the deoxycholate concentration to 0.19% resulted in separation of the microsomal material into five bands containing (in order from the top of the gradient) adenosine monophosphatase, inosine diphosphatase and some glucose-6-phosphatase (band 1); NADH-linked (band 2) and NADH-linked (band 3) electron transport enzymes; and glucose-6-phosphatase (bands 4 and 5). It appears that enzymes are arranged in specialized patches in the microsomal membrane.

Antigenic analysis of Neisseria gonorrhoeae by crossed immunoelectrophoresis

Crossed immunoelectrophoresis was used to study two complex antigenic preparations from Neisseria gonorrhoeae, one of cytoplasmic origin and the other derived by Triton X-100 extraction of isolated washed gonococcal envelopes, with the aim of developing suitable reference antigen-antibody systems that could be subsequently used to investigate the immune response to gonococcal infection and to monitor envelope preparations for cytoplasmic contamination. A number of parameters were investigated to optimized and standardize antigen preparation, e.g., harvesting and washing of gonococci, methods of bacterial disruption, and washing of envelopes. The effects of Triton X-100 concentration, initial total envelope protein concentration, and the composition, pH, and concentration of buffer on cell envelope extractability were studied to obviate the need to concentrate material before use in crossed immunoelectrophoresis. The electroendoosmotic properties of agarose were a major determining factor in resolving envelope antigens. From 25 to 30 immunoprecipitates were revealed in the envelope antigen-antibody system; 75 to 80 were revealed in the cytoplasmic sytem. Envelope immunoprecipitates with reduced nicotinamide adenine dinucleotide and lactate dehydrogenase activities were identified. Crossed immunoelectrophoresis with intermediate gels revealed the presence of antibodies in a preimmune rabbit antiserum pool to a distinctive fact-moving component in both the envelope and cytoplasmic antigen preparations. The intermediate gel technique also demonstrated that extensive washing of envelope preparations with buffer did not remove cytoplasmic ontamination completely. The method provides a much more sensitive means of monitoring the purity of envelope fractions than the use of single enzy,e markers as indexes of such contamination. The use of rabbit antisera raised to formolized gonococci in intermediate gels indicated that both reference antigen-antibody systems were of potential use in screening immune responses to N. gonorrhoeae.

Epinephrine-binding plasma-membrane antigens in rat liver

Detergent extracts of isolated rat liver plasma membranes were analysed in two-dimensional immunoelectrophoresis against antiserum to plasma membranes. Enzyme staining of the immunoprecipitates revealed the presence of about ten antigens with nucleoside di- and triphosphatase activity. Most of these were earlier shown also to be NADH-neotetrazolium reductase active. In addition, two of these antigens exhibited L-leucyl-beta-naphthylamidase activity. As judged from autoradiography these plasma membrane antigens earlier characterized as multienzyme complexes bound [14C]epinephrine, and the same antigens were labelled regardless of whether membranes or membrane extracts were incubated with the radioactive hormone. The specificity of this binding was established in displacement experiments with unlabelled hormones or their analogues. Another hormone-binding antigen, also identified in the plasma membrane extract did not exhibit any known enzyme activity while three antigens with different enzyme activities had no epinephrine-binding capacity. [14C]Epinephrine-labelled plasma membrane extracts were chromatographed on Sepharose 4B and the fractions obtained were analysed in two-dimensional immunoelectrophoresis combined with autoradiography. Nucleoside di- and triphosphatases of high molecular weights (5000000) were associated with L-leucyl-beta-naphthylamidase activity, while no such associations were detected in a lower molecular weight region (70000). Further immunological studies on the various fractionated antigens provided evidence that at least two of them occurred in both low and high molecular weight fractions. Hormone-binding membrane components in varying concentrations were found throughout the eluted extract.

Soluble and membrane-bound enzyme-active antigens of rat-liver lysosomes

Secondary lysosomes were isolated from rat liver and separated into a soluble and a membrane fraction. Plasma membranes and microsomes were also isolated and antisera against the various fractions were prepared in rabbits. Lysosomal content and detergent-solubilized membrane fractions were analysed in two-dimensional immunoelectrophoresis (crossed immunoelectrophoresis). The immunoprecipitates were stained by histochemical procedures for different enzyme activities such as phosphatases, non-specific esterase, arylsulphatase, glycosidases and L-leucyl-beta-naphthylamidase. When lysosomal content was tested against its corresponding antiserum, 17 different precipitates could be seen. Most of the enzyme activities tested were shown to reside separately in one or a few precipitates each. In contrast, when the membrane extracts were investigated, a more polymorphic pattern of enzyme-active precipitates appeared. Thus, when lysosomal membrane extracts were reacted with homologous antiserum 11 precipitates with acid phosphatase activity were obtained. Several of the antigens were electrophoretically different and immunologically non-identical. As expected from the biology of secondary lysosomes, many of their antigens were also found in microsomes and/or plasma membranes, but several antigens unique for lysosomes were detected concomitantly. Closer analysis of these results indicated that several seemingly identical enzyme-active proteins occurred both in soluble and membrane-associated forms. However, while many of the membrane antigens expressed 2-4 different enzyme activities, only one activity was detected in individual precipitates of the lysosomal content. Thus, acid phosphatase activity was found together with esterase activity in three membrane-associated antigens. The precipitates formed by two of these also stained for arylsulphatase and nucleoside tri-, di- and monophosphatase activities. L-Leucyl-beta-naphthylamidase activity was found in one additional acid-phosphatase-active precipitate.