Bone enzymes

Bone enzymes are direct products of active osteoblasts (bone ALP) and osteoclasts (tartrate-resistant acid phosphatase). 

and kidney isoforms of ALP are posttransiational modifications of the same gene product and are identified by their unique carbohydrate content (see Fig, 21-4). They have been described above in the section on liver enzymes. Bone ALP is produced by the osteoblast and has been demonstrated in matrix vesicles deposited as buds derived from the cell s membrane. The enzyme is therefore an excellent indicator of global bone formation activity 

In general, separation of tissue-nonspecific ALP forms (i.e., bone and liver) is difficult because of structural similarity. Bone ALP in serum can be measured by heat inactivation (a poor method), lectin precipitation, and immunochemical and electrophoretic methods (see the section on liver enzymes). 

Immunoassays for bone ALP, which measure either enzyme activity or mass, are commercially available crossreactivity with liver isoform however, has been established  

This general limitation should be borne in mind when interpreting test results. 

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Wergedal, J. E. Enzymes of protein and phosphate catabolism in rat bone. Enzyme property in normal rat. Calc. Tiss. Res. 3, 55 (1969)... 

Inactivation of human tissue phosphatases by urea was extensively studied by Posen and colleagues 98). At 37° placental phosphatase had a half-life of 3 hr in 8 M urea while the bone enzyme in 3 M urea had a half-life of only 7 min. Intestinal phosphatase was intermediate in stability. It was also reported that the catalytic activity of placental phosphatase is substantially lower in 8 M urea. 

The application of quality control procedures to ensure that satisfactory analytical performance of enzyme assays is maintained on a day-to-day basis is complicated by the tendency of enzyme preparations to undergo denaturation with loss of activity. This maltes it difficult to distinguish between poor analytical performance and denaturation as possible causes of a low result obtained for a control sample introduced into a batch of analyses. Assured stability within a defined usable time span is therefore the prime requirement for enzyme control materials, as it is for enzyme calibrators. However, specifications for the two types of materials can differ in other respects. Because the function of a calibrator is to provide a stated activity under defined assay conditions, it is not necessary for it to show sensitivity to changes in the assay system identical to those of the samples under test therefore within certain Umits, enzymes from various sources can be considered in the search for stability. However, it is the function of a control to reveal small variations in reaction conditions, so it must mimic the samples being analyzed. The preparation of enzymes from human sources is not by itself a guarantee of an effective control. For example, human placental ALP is very stable, but it differs significantly in kinetic properties from the liver and bone enzymes that contribute most of the ALP activity of human serum samples it is therefore not an ideal enzyme for use in control material for the determination of ALP. 

Elevations in serum ALP activity commonly originate from one or both of two sources the liver and bone. Consequently, serum ALP measurements are of particular interest in the investigation of two groups of conditions hepatobiliary disease and bone disease associated with increased osteoblastic activity (see Bone Enzymes section later in this chapter). 

Our data support the statement that the heat sensitivity of each enzyme source remains characteristic and independent of the influence of the others in the mixture, and that the resultant heat inactivation is an additive function of the heat-sensitivities of members of the mixture. Bone enzyme from different sources is very consistently heat-sensitive (85-90%), unlike intestinal (50-65%), and liver enzyme (50-75%). However, the heat sensitivity of the LPSAP of normal serum can vary from 33 to 85% and of the non-LPSAP fraction from 50 to 95%. Therefore one cannot determine the identity of the organ sources of serum alkaline phosphatase with a knowledge of only the heat sensitivity and the total alkaline phosphatase. However, by correcting the heat-inactivation of serum by that contributed by intestinal component, one obtains the heat-inactivation of non-intestinal sources of alkaline phosphatase. If this value is 90% or more, the non-intestinal component could be presumed to be of osseous origin if 60% or less, of hepatic origin. 

R14. Robison, R., and Soames, K. M., Possible significance of hexosephosphoric esters in ossification. III. Action of the bone enzyme on the organic phosphorus compounds in blood. Biochem. J. 18, 755-764 (1924). 

VI. Vaes, G., and Jacques, P., Studies on bone enzymes. The assay of acid hydrolases and other enzymes in bone tissue. Biochem. J. 97, 380-388 (1965). 

Laser desorption methods are particularly useful for substances of high mass such as natural and synthetic polymers. Glycosides, proteins, large peptides, enzymes, paints, ceramics, bone, and large... 

Another dideoxypyrimidine nucleoside active against human immunodeficiency vims is 3 -azido-2/3 -dideoxyuridine [84472-85-5] (AZDU or CS-87, 64) C H N O. Since its synthesis, (167) CS-87 has been identified as a promising antiHIV agent (168) and is currentiy undergoing phase I clinical trials in patients with AIDS and AIDS-related complex. It appears to be less potent than AZT against HIV in a peripheral blood mononuclear (PBM) cell screening system and in MT-4 cell lines. This lower activity in PBM cells appears to be related to a lower affinity of CS-87 for the enzyme responsible for its initial phosphorylation (169). However, CS-87 has significantly lower toxicity on bone marrow cells than AZT (170) and penetration of the CNS as a 5 -dihydropyridine derivative. 

As regards toxicity, pyrazole itself induced hyperplasia of the thyroid, hepatomegaly, atrophy of the testis, anemia and bone marrow depression in rats and mice (72E1198). The 4-methyl derivative is well tolerated and may be more useful than pyrazole for pharmacological and metabolic studies of inhibition of ethanol metabolism. It has been shown (79MI40404) that administration of pyrazole or ethanol to rats had only moderate effects on the liver, but combined treatment resulted in severe hepatotoxic effects with liver necrosis. The fact that pyrazole strongly intensified the toxic effects of ethanol is due to inhibition of the enzymes involved in alcohol oxidation (Section 4.04.4.1.1). 

The folate antagonists, pyrimethamine and sulfadiazine, inhibit the parasite s DHFR/TS synthase enzyme complex and the DHPS, respectively (Fig. 4) (see antimalarial drugs). To avoid deficiency of folic acid in patients treated with antifolate antagonists, folinic acid supplementation is recommended to reduce bone-marrow suppression. 

Zinc and cadmium have an oxidation number of +2 in all their compounds. Zinc is an essential element for human health. It is present in many enzymes and plays a role in the expression of DNA and in growth. Zinc is toxic only in very-high amounts. However, cadmium is a deadly poison that disrupts metabolism by-substituting for other essential metals in the body such as zinc and calcium, leading to soft bones and to kidney and lung disorders. 

Some of the critical enzymes in our cells are metalloproteins, large organic molecules made up of folded polymerized chains of amino acids that also include at least one metal atom. These metalloproteins are intensely studied by biochemists, because they control life and protect against disease. They have also been used to trace evolutionary paths. The d-block metals catalyze redox reactions, form components of membrane, muscle, skin, and bone, catalyze acid-base reactions, control the flow of energy and oxygen, and carry out nitrogen fixation. 

Child, A.M., Gillard, R.D. and Pollard, A.M. 1993 Microbially-induced promotion of amino acid racemization in bone isolation of the microorganisms and the detection of their enzymes. Journal of Archaeological Science 20 159-168. 

Carnivores rely on a protein-rich diet and produce new biomass primarily from dietary amino acids, although the enzymes required for de novo amino acid synthesis are present (Garmes et al., 1998). Bone collagen, muscle (meat) and apatite were analyzed for a set of modern southern African herbivores and carnivores (Lee-Thorp et al., 1989). The isotopic analyses showed i C enrichment in bone collagen, apatite and muscle, and depletion in lipids. Difference in values between herbivores and carnivores indicates a trophic effect, which for carbon in bone collagen is 2.5-3%o (Fig. 2). 

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