Elevated glycosidases and proteolytic enzymes in cells transformed by RNA tumor virus

Microenvironmental Regulation of the Initiated Cell

In the classical skin model of tumor initiation, keratinocytes treated once with carcinogen retain their normal appearance and growth behavior indefinitely unless promoted to growth into papillomas. Because many of the papillomas regress and may recur with further promotion, their cells can also be considered as initiated. The growth of initiated keratinocytes can be inhibited either in vitro or in vivo by close association with an excess of normal keratinocytes, but it is enhanced by dermal fibroblasts. Chick embryo fibroblasts (CEF) in culture produce transformed foci after infection with Rous sarcoma virus (RSV) on a background of normal CEF in a medium containing 10% or less calf serum (CS), but they retain normal appearance and growth regulation in 10% fetal bovine serum (FBS) or 20% CS. Transformation of a carcinogen-treated line of mouse embryo fibroblasts is prevented, and can be reversed, in high concentrations of FBS in the presence of an excess of normal cells. FBS has high, broad-spectrum antiprotease activity. Increased protease production occurs in a variety of transformed cells and is correlated with progression in tumors. Protease treatment stimulates DNA synthesis and mitosis in confluent, contact-inhibited normal cell cultures. Synthetic inhibitors of proteases suppress transformation in carcinogen-treated cultures and inhibit tumor formation in animals. Several different classes of protease may be overexpressed in the same transformed cells. It is proposed that excessive protease production accounts for major features of neoplastic transformation of initiated cells, but that transformation can be held in check by protease inhibitors present in serum and released from surrounding cells. It would be informative to determine whether high concentrations of FBS would inhibit the neoplastic development of initiated keratinocytes.

Studies of the activities of lysosomal enzymes in serum and buccal pouch tissue of hamsters during 7,12-dimethylbenz[a]anthracene-induced carcinogenesis

Alterations in the activities of certain lysosomal enzymes such as beta-D-galactosidase, beta-D-glucosidase, beta-D-glucuronidase, alpha-L-fucosidase, N-acetyl-beta-D-glucosaminidase, cathepsins B and D were studied in serum and tissue homogenates of buccal mucosa of hamsters treated with 0.5%, 7,12-dimethylbenz[a]anthracene (DMBA) in liquid paraffin. Among the enzymes studied, the activities of beta-D-galactosidase and N-acetyl-beta-D-glucosaminidase showed significant elevation both in serum and tissue homogenates fro papilloma onwards and the elevations were progressive with the development of carcinomas. The elevations in the activities of alpha-D-fucosidase and cathepsin D were found to be significant from papillomatous tissue onwards whereas in serum they showed higher activities only in carcinoma stages. The activities of beta-D-glucosidase, beta-D-glucuronidase and cathepsin B in both serum and in tissue homogenate were elevated markedly only in carcinoma stages. It is suggested that beta-D-galactosidase and N-acetyl-beta-D-glucosaminidase may be used as diagnostic markers for premalignant and malignant lesions of oral mucosa.

Effect of radiation on serum glycoproteins and glycosidases in patients with cervical carcinoma

OBJECTIVE

The serum glycan moieties of glycoproteins and the activities of glycosidases were analyzed in order to elucidate the metabolism of glycoprotein in uterine cervical cancer.

METHODS

Serum was collected from patients at different stages of cervical cancer before and after treatment. The results were analyzed using Student's t-test.

RESULTS

The glycan moieties such as sialic acid and fucose were significantly elevated even in the early stages of carcinoma, whereas a significant elevation in hexose and hexosamine levels was observed only in the advanced stages. Among the investigated lysosomal glycohydrolases, beta-D-galactosidase, N-acetyl-beta-D-glucosaminidase and alpha-L-fucosidase activities were elevated significantly at all stages except for stage I. The altered levels of glycoproteins and glycosidases were reduced to near-normal levels after radiotherapy.

CONCLUSION

The levels of glycan moieties and the activities of glycosidases can be used as diagnostic markers to assess the stage of cancer and can be used as prognostic markers during therapy.

Neoplastic alteration of a membrane-associated sialidase of rat liver

Rat liver particulate fraction contains two types of membrane-associated and gangliosides-hydrolyzing sialidase, which have been shown to be identical to two membrane-associated sialidases of rat brain (I and II) chromatographically, immunologically and in substrate specificity. Chromatography on AH-Sepharose 4B of the membrane sialidases of rat primary hepatoma induced by 3'-methyl-4-dimethylaminoazobenzene (MeDAB) further revealed that hepatocarcinogenesis induces a marked decrease in sialidase II but no decrease in sialidase I. Using antisera against sialidases I and II of rat brain, immunoprecipitation studies of the solubilized particulate fractions of rat liver and MeDAB-hepatoma gave results similar to those obtained chromatographically. Using the same immunological technique, sialidase II but not sialidase I was found to be decreased in AH109 A hepatoma and in regenerating and fetal liver.

Phosphohexose isomerase in hypernephroma. Significance as serum tumor marker, comparison to other glycolytic enzymes and isozyme patterns in normal and tumor tissue

In hypernephroma an overall diagnostic sensitivity of 72% and a specificity of 87% was found for the serum tumor marker phosphohexose isomerase (PHI). Both in early stage disease and in well differentiated tumors a sensitivity of about 60% was reached. In contrast the sensitivity of three other glycolytic enzymes tested was found to be less than 20%. Since the cancer induced elevation of PHI activity in the tumor was found to be comparable to those of the other test enzymes, elevated PHI serum activities cannot be attributed to overproportional PHI synthesis and unspecific cell-lysis. In 6 of 10 cases studied differences in the PHI isozyme pattern between the tumor and the normal tissue were found suggesting the occurrence of cancer associated structural alterations of PHI.

Significance of glycosidases and phosphatases in Cercopithecus and Macaca cells

When selected ratios of different glycosidases and phosphatases from primary monkey kidney cells or from monkey kidney cell lines are presented graphically, characteristic patterns do evolve. Three different subtypes of Vero cells show similar glycosidase patterns. The Vero subtypes tested show glycosidase patterns that are closely similar to those of primary cells of Cercopithecus aethiops. Glycosidase patterns of BS-C-1 and CV-1 cells are less similar to those of primary Cercopithecus cells than are those of Vero cells. Primary kidney cells from Macaca cynomolgus show significantly different glycosidase patterns compared with those of different Cercopithecus cells. The distinct glycosidase patterns can be used to classify the tested cell lines in relation to each other.

Involvement of protease in L-glutamine control of nucleic acid and polyphosphate metabolism in cells transformed by 9,10-dimethyl-1,2-benzanthracene, SV40 and H-ras oncogene

Mammalian cells transformed with either 9,10-dimethyl-1,2-benzanthracene, SV40 or H-ras oncogene dramatically changed their ability to synthesize DNA and RNA and metabolize polyphosphate when L-glutamine was withdrawn from the growth medium or when heat shocked (growth at 42 degrees C). Untransformed, DNA and RNA synthesis decreased by 50-80% when glutamine was withdrawn, but polyphosphate accumulated whether or not glutamine was supplied. Heat shock did not alter this response. Transformed isogenic cells responded differently; at 37 degrees C, they decreased their synthesis of DNA and RNA if starved for glutamine, whereas at 42 degrees C, synthesis was optimal without glutamine. Transformed cells accumulated polyphosphate at 37 degrees C when starved for glutamine, but at 42 degrees C, no polyphosphate accumulated. This apparent non-dependence on glutamine by transformed cells when heat shocked was found to be due to the production of glutamine from serum proteins through induction of a protease(s).

Inhibition of glycosylation prevents H-2K and D antigen expression on SV40 virus-transformed cells

Tunicamycin, an inhibitor of glycosylation, was used to examine the role of carbohydrate moieties of glycoproteins involved in recognition of Simian virus 40 (SV40)-transformed cells by cytotoxic T lymphocytes (CTL). Tunicamycin treatment renders such cells refractory to lysis by H-2 restricted, SV40-specific CTL as well as by allogeneic CTL directed only against H-2 antigens. Treated cells are no longer susceptible to lysis by anti-H-2 antisera and complement, nor are they stained by monoclonal anti-H-2 antibodies in an indirect immunofluorescence assay. No accumulation of H-2 proteins was detected in immunoprecipitates from cells labeled with [35S]methionine in the presence of tunicamycin. It is concluded that tunicamycin prevents the expression of H-2 glycoproteins in these cells, perhaps due to accelerated degradation of the unglycosylated molecules.

Approach to the mechanism of Zajdela's hepatoma cell growth inhibition induced by concanavalin A and phytohaemagglutinin

Cell growth of tumour ascites cells was inhibited by concanavalin A, phytohaemagglutinin and Ricinus lectin at 2-100 micrograms/ml. As expected, the Ricinus lectin inhibited the protein synthesis estimated by leucine incorporation and decreased thymidine incorporation, whereas concanavalin A and phytohaemagglutinin stimulate the uptake and the incorporation of both leucine and thymidine, and thus, synthesis of protein and DNA. These results suggest that different mechanisms are involved in the hepatoma cell growth inhibition by the lectins. This difference was not related to the kinetic characteristics of the lectin interactions with the cells which represent a first and necessary step. It was showed that concanavalin A and phytohaemagglutinin as well as chloroquine inhibited the 14C-labelled asialofetuin degradation. We can conclude that Ricinus lectin present a toxic effect whereas both concanavalin A and phytohaemagglutinin show an anti-protease activity.

Biochemical activities of lysosomal acid hydrolases in leukemic cells

The biochemical activities of 8 lysosomal acid hydrolases in leukemic cells from 48 patients were examined. Characteristic alterations were found in alpha-mannosidase, beta-galactosidase and N-acetyl-beta-glucosaminidase activities of leukemic cells. The level of alpha-mannosidase activity was much higher in myelo(mono)genous leukemias (AML, AMoL, AMMoL, CML and CMMoL) than in lymphogenous ones (ALL, T-cell leukemia, hairy cell leukemia and CLL) without exception. The beta-galactosidase activity also differed as a result of alpha-mannosidase, except in T-cell leukemia. In T-cell leukemia it was within the range of normal lymphocytes, but in the other lymphogenous leukemias it was significantly below normal. N-acetyl-beta-glucosaminidase activity in myelo(mono)genous leukemic cells was above the range of normal granulocytes. The changes in these enzyme levels were consistent. The lymphocytic or myelocytic nature of three cases of acute undifferentiated leukemia could be determined by enzyme studies. In two cases it was lymphocytic and in one it was myelocytic. The enzymatic abnormalities were also found in morphologically mature neutrophils from patients but not only chronic types (CML, CMMoL) but also acute types (AMoL, AMMoL) of leukemias, and were similar to those of their respective leukemic cells. Analysis of lysosomal enzymes (at least three of those mentioned above), can elucidate one of the biochemical properties of leukemic cells and may be valuable in the differentiation of leukemias.

Enhancement of cartilage protease activity during age and growth hormone-dependent growth

We wish to report an intriguing relationship between cartilage protease activity and rat growth rate. This was demonstrated by comparing protease activities of rats having different growth rates, i.e., normal rats of different ages, hypophysectomized and growth hormone-treated hypophysectomized rats. Protease activity, assessed by hydrolysis of a gelatin film by cartilage microtome slices, at pH 4.0, was time and temperature dependent. Preincubation of cartilage tissue at various temperatures resulted in an increase of protease activity from 4 degrees C to 37 degrees C and a decrease in activity from 37 degrees C to 100 degrees C. The activity of younger (4 week old) more rapidly growing rats, was greater than that of older, less rapidly growing animals. Hypophysectomy reduced protease activity to approximately one-third normal levels. However, injection of bovine growth hormone into hypophysectomized rats restored the activity. These results suggest that a positive correlation exists between cartilage protease activity and growth rate. Our results support the novel hypothesis that cartilage growth could be mediated, at least in part, via growth hormone-dependent proteolytic activity.

Acid glycosidases in basal cell epithelioma and in seborrhoeic keratosis

Total activities of eleven glycosidases were determined in frozen-dried tissue fragments of basal cell epithelioma, seborrhoeic keratosis and epidermis. The values found were frequently much higher than those mentioned in the literature. Most enzyme activities were higher in basal cell tumours than in the adjacent epidermis; the differences between basal cell epithelioma and seborrhoeic keratosis were significant for only two of the eleven enzymes.

An investigation in vitro of the exocytosis of lysosomal enzymes from C6 glioma cells

The rates of exocytosis on the lysosomal hydrolase n-acetyl-beta D-glucosaminidase and beta-glucuronidase were measured in monolayer cultures of the C-6 glioma cell line. A comparison of the kinetics of release of the enzymes and the effects of cytochalasin B suggest that either intralysosomal localisation or the mechanism of release may be different for each enzyme. Evidence was obtained that exocytosis is accompanied by receptor-mediated endocytosis of hydrolases and the importance of the microtubular system in the maintenance of the exocytosis equilibrium was indicated by the effect of colchicine on the rate of extracellular accumulation of the enzymes.

Studies on cell adhesion and recognition. III. The occurrence of alpha-mannosidase at the fibroblast cell surface, and its possible role in cell recognition

The occurrence of alpha-mannosidase activity at the surface of hamster embryo (NIL) fibroblasts is indicated by the following findings: (a) When NIL cells were incubated on the glass surfaces on which ovalbumin glycopeptides were covalently linked, a rapid release of free mannose from ovalbumin glycopeptides was observed as evidenced by analysis on gas chromatography/mass spectrometry. (b) Cell suspensions as well as intact cell monolayers hydrolyzed rapidly p-nitrophenyl-alpha-D-mannoside, and the time-course of the hydrolytic cleavage was linear from the moment of mixing of the substrate with the cells. The hydrolysis of the nitrophenyl glycosides of beta-D-mannose, alpha-D-galactose, beta-D-galactose, alpha-L-fucose, beta-D-glucose, beta-D-N-acetylgalactosamine and beta-D-N-acetylglucosamine was negligible or more than ten times lower as compared with the hydolysis of alpha-D-mannoside. (c) No released or secreted activity of mannosidase could be detected under the conditions used. (d) Studies using known proportions of broken cells in the incubation mixture indicated that more than 90 percent of the mannosidase activity measured was attributable to intact cells and not to broken cells or cell fragments. (e) Hydrolysis of p-nitrophenyl-alpha-D-mannoside by cell monolayers was inhibited, in the order of decreasing inhibitory activity, by yeast mannan, ovalbumin, alpha-1,4-L-mannonolactone, alpha-methylmannoside, and mannose-6-phosphate. High inhibitory activity of the mannan polysaccharide and of ovalbumin favored the presence of the mannosidase activity at the cell surface, as these substrates may not penetrate rapidly into the cells. The following findings indicated that the cell surface mannosidase is mediating the cell adhesion based on the recognition of high-mannose-type glycopeptide: (a) Ovalbumin- coated plastic surfaces strongly promoted attachment and spreading of NIL fibroblasts, whereas the same ovalbumin coat did not promote attachment and spreading of some other cell types (BALB/c 3T3 fibroblasts and freshly prepared rat liver cells). (b) Digestion of ovalbumin with alpha-mannosidase greatly reduced the adhesion-mediating activity. (c) Cell adhesion to ovalbumin-coated surfaces was strongly inhibited by mannose tetrasaccharides, moderately by alpha-1,4-L-mannonolactone, and weakly by alpha- methylmannoside and mannose-6-phosphate. This order of the inhibitory activity for cell attachment is the same as that for the inhibition of mannosidic hydrolysis. The interpretation that the cell surface mannosidase is able to mediate cell adhesion is in agreement with previous studies suggesting that polyvalent glycosidase surfaces can promote cell adhesion to a degree similar to that caused by fibronectin and several lectins by interacting with their cell surface substrate site (the accompanying papers of this series).

The use of con A Sepharose as an affinity adsorbent in a simple assay of serum sialyl and fucosyltransferase and its application in tumour diagnosis

A considerably simplified assay for recording sialyl- and fucosyltransferase in human serum is presented. Serum samples incubated with labeled nucleotide-sugar and glycosylated endogenous acceptor molecules were adsorbed to Con A Sepharose and quantitated by scintillation counting. The results correlated with those of a much more time consuming acid precipition method, and displayed a higher diagnostic sensitivity due to the improved specificity of the method and the combined recording of the two activities. A correlation between serum sialyl- and fucosyltransferase activities as well as quantitative agreement between the amount of incorporated sialic acid and fucose indicated that rhe endogenous acceptor molecules were rate-limiting for transfer and may themselves have diagnostic potential.

Isolation of alpha 1-protease inhibitor from human normal and malignant ovarian tissue

Proteolytic enzymes are associated with normal and neoplastic tissues. Therefore protease inhibitors might also be involved in the control of cell function. alpha 1-protease antigen and antitryptic activity have been found in normal and neoplastic human ovarian homogenate. The inhibitor has been localized to ovarian stromal cells or tumor cells by immunoperoxidase staining. The protein was purified to apparent homogeneity as judged by alkaline gel and sodium dodecyl sulfate (SDS) gel electrophoresis. Immunochemical studies revealed antigenic similarity of plasma alpha 1-protease inhibitor by double immunodiffusion and similar mobility on immunoelectrophoresis and two-dimensional electroimmunodiffusion. The molecular weight was similar to that described for plasma alpha 1-protease inhibitor: 60,000 by gel filtration and 53,500 by SDS electrophoresis. Furthermore, the phenotypic pattern as determined by acid starch gel electrophoresis and immunoprecipitation was PiMM, which is the predominant genetic variant in normal plasma alpha 1-protease inhibitor. An inhibitor ws isolated and purified from an ovarian carcinoma that exhibited functional, immunochemical, and physical similarity to the normal ovarian alpha 1-protease inhibitor. alpha 1-protease inhibitor from normal and malignant ovaries competitively inhibited bovine pancreatic trypsin at incubation times of 5 min at 30 degrees C. Inhibition constant (Ki) values were calculated at 0.67 and 0.51 inhibitory units, respectively. The alpha 1-protease inhibitor in malignant cells may be a factor in the control of proliferation in this tissue. Since ovulation is in part a proteolytic event, the alpha 1-protease inhibitor in ovarian cells may play a role in the control of this specialized tissue. Persistance of this protein in malignant ovarian tissue may be a vestige of its differentiated origin.

Characterization of cell-surface glycopeptides from mouse cerebral cortex that inhibit cell growth and protein synthesis

Glycopeptides were isolated from the cell surfaces of mouse brain cortical tissue that inhibited both cell division and protein synthesis by cells in culture. The protein-synthesis inhibition appeared to affect most cells exposed and was equally effective against glycoprotein and protein synthesis. The inhibition of protein metabolism was independent of mRNA synthesis and uptake of labelled precursors into intracellular pools, indicating that it was directed at intracellular translational events. Fractionation of chloroform/methanol-extracted preparations of this brain cell-surface substance on Bio-Gel P-100 revealed the material to be quite heterogenous, although inhibitory activity was found only in fractions of mol.wt. 25000--30000 and 6000--10000. Biochemical analysis of these fractions demonstrated that they were 6% carbohydrate and 94% amino acid by weight. The 25000--30000-mol.wt. glycopeptides were shown to inhibit cell growth at concentrations of 2 microgram/ml in cultured cells and to inhibit protein synthesis by 50% at concentrations of 3 microgram/ml. The 25000--30000-mol.wt. brain-cell-surface-substance glycopeptides were further purified by ultrafiltration and affinity chromatography with Ulex europaeus agglutinin, resulting in a 400-fold increase in specific biological activity. The inhibitor was not lethal to cells and was not species- or tissue-specific.

Lysosomal hydrolases in long term cultures of human gliomas: total enzyme activities and rate of extracellular accumulation

A number of investigations have suggested a fundamental role for lysosomal enzymes in growth control of normal cells and in the loss of growth control which occurs in neoplasia and in cell cultures transformed by oncogenic viruses. In this investigation total enzyme activities and rates of extracellular accumulation of enzyme were measured in long term cultures of gliomas and normal human astrocytes. Marked differences were found between the cultures with regard to total enzyme activity. Exocytosis rates of the enzymes also showed differences, with one group of tumours demonstrating low or intermediate rates and another smaller group with high rates. There was no positive correlation between the enzyme profile of the cultures and their tumorigenicity in nude mice.

Proteolytic enzymes in normal and transformed cells

Virally transformed cells show an increased production of proteolytic enzymes. These might be involved in transformation-dependent alterations of cell surface glycoproteins. The possibility arises that some of these proteases might be membrane-bound. To investigate this possibility, we have undertaken a comparative study of the reactivity of intact normal and transformed cells with the tritium labelled protease inhibitor diisopropylfluorophosphate, in parallel with fibrinolytic assays. Using these two approaches in concert, it was possible to identify and localize in the transformed cells several proteases which were present in the particulate cell fraction and were probably membrane bound. In particular, a diisopropylfluorophosphate-reactive polypeptide of 62,000 was increased 5--8-fold on transformation. It comigrated with a fibrinolytic activity. Other particle-bound activities were also detected. While diisopropylfluorophosphate-labelling can be useful for detecting proteases inside cells, it does not appear to be specific for surface proteases.

Lactoperoxidase-catalysed iodination of surface proteins on human melanoma cells

The cell-surface proteins of 6 different melanoma cell cultures have been labelled with 125I using lactaperoxidase-catalysed iodination. Fractionation of the proteins was achieved using 5--22.5% polacrylamide-gradient gel electrophoresis in the presence of sodium dodecyl sulphate (SDS) and the proteins were detected by autoradiography. Up to 24 labelled proteins were detected in the individual cell cultures, but the proteins labelled differed considerably in the 6 cultures examined. A possible reason for this, involving variation in the glycosylation of cell-surface glycoproteins is discussed. Cells of the same melanoma line had similar cell-surface proteins at different passage levels, but changes in the labelled proteins occurred when the culture conditions were altered. The cell-surface proteins of high molecular weight were cleaved by trypsin, but most of the low mol.-wt. proteins were resistant to trypsin. The "large external transformation sensitive" (LETS) protein detected as a major protein on fibroblasts in culture was not a dominant protein on the melanoma cells. It was detected on only 4/6 cell cultures. Possible relationships of the cell-surface proteins described in this study to morphology, immunological properties and proteolytic activity of human melanoma cells are discussed.

Partial characterization and proposed mode of action of inhibitory HeLa cell surface polypeptides

Polypeptides removed from the HeLa cell surface by mild pronase treatment rapidly inhibit protein synthesis when added to HeLa cells or cell-free translation systems derived from HeLa cells. The inhibitory activity is heat stable. Protein and carbohydrate components of these polypeptides are required for inhibition of protein synthesis in vivo and in vitro. Two peaks of activity can be recovered from polyacrylamide gels, corresponding to polypeptides with molecular weights of approximately 29 000 and 41 000. Inhibition of protein synthesis in cell-free translation systems appears to be primarily an effect on elongation of polypeptide chains, whereas in the intact cell the primary target may be polypeptide chain initiation.

Fibrinolytic activity associated with cultured human neoplastic and normal cells

Fibrinolytic activity was studied in a number of different established as well as secondary human cell cultures derived from both malignant and normal tissues. The ability to degrade [25I]-labeled fibrin was found to be characteristic of some malignant cultures as well as some normal cultures, and to be dependent upon the presence of serum. For the most part, this activity was detected in cultures with a relatively short in vitro passage history (less than 30 passages). Low passaged colon and rectal carcinoma cells, HCT-8 and HRT-18, as well as normal rectal, colon and foreskin fibroblasts were positive for fibrinolytic activity, while long established (greater than 100 passages) cultures of malignant cells (colon carcinoma, HeLa, Hep-2, KB) as well as normal cells (HEI, AV3) were negative. It is proposed that although some normal cells synthesize plasminogen activators, the fibrinolytic capability of both malignant and normal cells may be lost on prolonged in vitro cultivation.

Lysosomal hydrolases of the epidermis. 6. Changes in disease

The activities of 14 acid hydrolases have been measured in normal and diseased human epidermis. Our findings were as follows: (i) Increased hydrolase activity was common in lesions; the clinically uninvolved skin of patients, however, invariably showed normal values. (2) The pattern of change was independent of the nature of the didease, the arylsulphatases and beta-glucosidase usually showing the greatest elevations. (3) The magnitude of the changes differed from disease to disease, being most marked in the lesions of psoriasis. (4) Ichthyosiform erythroderma was exceptional in showing elevated levels of the galactosidases and cathepsins B1 and D. We suggest that (with the exception of ichthyosiform erythroderma) the abnormalities which we have observed may be related to the proliferative rate of the epidermis.

The demonstration of acid phosphatase in cultured 3T3 mouse cells

Acid phosphatase has been demonstrated ultrastructurally in 3T3 and SV40-3T3 mouse cells using sodium beta-glycerophosphate and p-nitrophenyl phosphate as substrate. The former substrate only demonstrates the enzyme in lysosomes and elements of the Golgi apparatus while the latter demonstrates it in the cisternae of the endoplasmic reticulum and in the cell surface as well as at lysosomal sites. The significance of surface acid phosphatase activity is discussed in terms of sublethal autolysis.