Lysosomal acid phosphatase

The acid phosphatase activities were also determined in brain, kidney, liver, and spleen taken at autopsy from the patient and, like the acid phosphatase activities of lymphocytes and the fibroblasts, was found to be virtually absent, certainly less than about 2% of the activities in the corresponding tissues of the control individuals. Lymphocytes obtained from whole blood showed essentially the same acid phosphatase activity in the heterozygotes as in the controls. However, after 56 hours of stimulation with phytohemagglutinin (PHA), the acid 

Acid Phosphatase Activity op Cultivated Fibboblasts in Lysosomal Acid Phosphatase Deficiency  

Subjects Original homogenate Lysosomal fraction Lysosomal fraction + Triton 

---

Nadler, H. L. and Egan, T. J. "Deficiency of Lysosomal Acid Phosphatase a New Familial Metabolic Disorder". 

The lysosomal acid phosphatase was cytochemically shown to be present in dense bodies of chondrocytes but not in the nearly matrix vesicles461,462). Subsequent studies have confirmed that the amount of acid phosphatase in isolated vesicles is low and also that the activities of -glucuronidase and cathepsin D in the isolated vesicles were negligible463). The evidence indicates that matrix vesicles are not lysosomal. Isolated vesicles contain comparatively little mitochondrial succinic dehydrogenase, suggesting that the matrix vesicles and mitochondria were not identical458). 

CoA undergoes dephosphorylation, catalyzed by lysosomal acid phosphatase, to dephospho-CoA, followed by pyrophosphatase action to release 4 -phosphopantetheine and 5 -AMP - the reverse of the final stages of CoA synthesis shown in Figure 12.2. CoA is also a substrate for direct pyrophosphatase action, at about 10% of the rate of action on dephospho-CoA. The pyrophosphatase seems to be a general nucleotide pyrophosphatase of plasma membrane rather than an enzyme specific for the degradation of CoA. 

Figure 9-14. Frequency distribution of various marker enzymes for lysosomes (acid phosphatase, cathepsin, etc.), peroxisomes (urate oxidase) and mitochondria (cytochrome oxidase). Mitochondrial fraction from rat liver centrifuged in a linear gradient of 0.25 to 0.5M sucrose. [From H. Beaufay et al., Biochem. /., 73 628 (1959).]...

That the properties of lysosomal acid phosphatase do not change upon solubilization was evident when the lysosomal fraction was subjected to alternate freezing and thawing for 10 times and then centrifuged at 100,000fif for 1 hour 50% of its acid phosphatase was released into the suspending medium, and the remainder was associated with the lysosomal membrane and precipitable. The patterns of hydrolysis of various substrates with the exception of G-6-P which reflected membrane-bound glucose-6-phosphatase, were the same for the two subtractions. 

The lysosomal acid phosphatase enzyme played a key role in the discovery of lysosomes by de Duve in 1963 and is widely used as a lysosomal marker. This enzyme shows a high degree of sequence similarity (ca. 49 % identity) with prostatic acid phosphatase [9] and both are inhibited by L-(+)-tartrate ion [10]. 

Peters C, Geier C, Pohlmarm R et al (1989) High degree of homology between primary structure of human lysosomal acid phosphatase and human prostatic acid phosphatase. Biol Chem Hoppe Seyler 370 177-181... 

Human lysosomal acid phosphatase cloning, expression and chromosomal assignment. EMBO J 7 2343-2350... 

S. Gottschalk, A. Waheed, B. Schmidt, P. Laidler, and K. von Figura, Sequential processing of lysosomal acid phosphatase by a cytoplasmic fliiol proteinase and a lysosomal aspartyl proteinase, EMBO J, 8 (1989) 3215-3219. 

In rats infected with aerosols of Staphylococcus aureus and then exposed for 5 h to 2.5 ppm of ozone, bacterial ingestion and clearance by alveolar macrophages were impaired due to the absence of lysosomal acid phosphatase and P-glucuronidase activities in those cells subjected to the dual insults (Goldstein et al. 1978). 

Alveolar macrophages obtained by bronchoalveolar lavage from 25 silicotic patients under the electron microscope showed silica particles, activated nuclei, autophagic vacuoles and destroyed cell organelles (Reisz et al. 1988). Lysosomal acid phosphatase activity was elevated as compared with healthy volunteers. 

Viewing the fact that only a portion (but not all of the acid phosphatase) of the lysosomal fraction is readily released upon physical disruption of the lysosomal membrane by freezing and thawing or by hypoos-motic pressure, Baccino et al. (1971) suggested that at least two varieties of acid phosphatase were associated with the lysosomal fraction, the first being readily, and the other not readily, dissociable from lysosomal structures. This interpretation coincides with the earlier observation of Sloat and Allen (1969) who showed two varieties of acid phosphatase associated with lysosomal fractions of rat liver. One form is readily released after physical disruption of lysosomal fractions, the other form is associated with the lysosomal membrane and became soluble only with 5% Triton X—100 treatment. This membrane-associated enzyme accounted for 40% of the total lysosomal acid phosphatase, is heat-stable, and can be separated from the soluble form by electrophoresis. But these two enzymes have similar pH optima and a common response to inhibitions by L-tartrate, fluoride, alloxan, and formaldehyde. 

Comparison of Substrate SpECiFicrnES of Microsomal and Lysosomal Acid Phosphatases of Mouse Kidney... 

The Triton X-100 solubilized microsomal acid phosphatase and the free lysosomal acid phosphatase also differ in elecfrophoretic migration rates with the lysosomal enzyme migrating faster in the polyacrylamide gel electrophoresis at an acid pH. These two enzymes can also be separated by DEAE-cellulose chromatography (Lin and Fishman, 1972). 

Similar observations regarding differences between the lysosomal and microsomal acid phosphatase have been reported in blood platelets (Walter et al., 1971 Kaulen and Gross, 1971). The lysosomal acid phosphatase of pig blood platelets splits preferentially yS-glycerophosphate, having a pH optimum at 5.1 and is relatively more stable at 50°C. The microsomal enzyme has a higher specificity for p-nitrophenyl phosphate, having a pH optimum at 6.0 and is less stable at 50 C. 

More problematic and more controversial is the biological role of uteroferrin. Present in allantoic fluid in concentrations often exceeding 2 mg/ml (5 X 10" M), it is hard to imagine an enzymatic function for this protein in the physiological compartment in which it abounds. Conceivably, it is simply leaked into the allantoic fluid by hyperproducing lining cells of the allantoic membrane, for which uteroferrin functions as a lysosomal acid phosphatase ). An alternative possibility is that uteroferrin functions not as an enzyme, since it is almost inactive at the pH of the fluid in which it is found, but as a carrier of iron from sow to fetal pig ). 

---