Lysozyme in preosseous cartilage VI. Purification, characterization and localization of mammalian cartilage lysozyme

Identification and localization of lysozyme as a component of eggshell membranes and eggshell matrix

The avian eggshell is a composite biomaterial composed of non-calcifying eggshell membranes and the overlying calcified shell matrix. The calcified shell forms in a uterine fluid where the concentration of different protein species varies between the initial, rapid calcification and terminal phases of eggshell deposition. The role of these avian eggshell matrix proteins during shell formation is poorly understood. The properties of the individual components must be determined in order to gain insight into their function during eggshell mineralization. In this study, we have identified lysozyme as a component of the uterine fluid by microsequencing, and used western blotting, immunofluorescence and colloidal-gold immunocytochemistry to document its localization in the eggshell membranes and the shell matrix. Furthermore, Northern blotting and RT-PCR indicates that there is a gradient to the expression of lysozyme message by different regions of the oviduct, with significant albeit low levels expressed in the isthmus and uterus. Lysozyme protein is abundant in the limiting membrane that circumscribes the egg white and forms the innermost layer of the shell membranes. It is also present in the shell membranes, and in the matrix of the calcified shell. Calcite crystals grown in the presence of purified hen lysozyme exhibited altered crystal morphology. Therefore, in addition to its well-known anti-microbial properties that could add to the protective function of the eggshell during embryonic development, shell matrix lysozyme may also be a structural protein which in soluble form influences calcium carbonate deposition during calcification.

Purification, characterization, and biosynthesis of bovine cartilage lysozyme isoforms

The cationic protein, lysozyme, has an extracellular distribution in cartilage; however, its biological role in this tissue still remains unclear. This study describes a simple and high yielding procedure for the purification of four novel isoforms of lysozyme from the functionally different articular (metacarpalphalangeal joint) and nonarticular (nasal septum) bovine cartilages. Chromatography of the cartilage extracts on S-Sepharose revealed the presence of four major lysozyme active peaks each of which was further purified to homogeneity by gel filtration and reversed-phase chromatography. Each peak yielded a different molecular mass when analyzed by ion spray mass spectrometry, and material isolated from either cartilage source displayed an identical molecular mass for each lysozyme preparation. N-terminal amino acid sequence and amino acid composition analyses confirmed the presence of four novel lysozyme isoforms in both bovine articular and nonarticular cartilages. The lytic activity of each lysozyme isoform toward Micrococcus lysodeikticus was dependent on both the ionic strength and pH of the buffer, where an increase in activity accompanied an increase in ionic strength. The lysozymes were shown to be synthesized by chondrocytes in vitro, which in addition to the relatively high chemical amounts of lysozyme present in cartilage, would suggest that this small cationic protein has some as yet undetermined biological role within the cartilage extracellular matrix.

Quantification of hen egg white lysozyme in cartilage by an enzyme-linked immunosorbent assay

We have developed an enzyme-linked immunosorbent assay (ELISA) with an inhibition step to quantify hen egg white lysozyme (HEWL) on a weight basis. The assay is relatively insensitive to changes in ionic strength or pH. Quantification is not affected by the presence or large amounts of mammalian lysozymes or inhibitors of enzymatic activity such as soluble chitin oligomers. We used this ELISA to show that the HEWL content of chick cartilages increases progressively between days 14 and 18 of embryonic life. The maturation-related increase does not appear to be the result of increased synthesis by the chondrocytes for the latter did not synthesize detectable amounts of lysozyme in vitro. Evidence was obtained to suggest that most, if not all, the lysozyme in cartilage is derived from the surrounding fluids which come in contact with the matrix.

Tissue specific deficiency of lysozyme in ruminants

The distribution of lysozyme in tissues and fluids of ruminants was examined and it was determined that, except for a few tissues, ruminants were deficient in lysozyme activity compared with other species. The prominent exception was the abomasum of cattle, which had high levels of lysozyme activity. Mixing and extraction studies indicated that the lysozyme deficiency of ruminants was due neither to the presence of inhibitors of lysozyme in ruminant tissue nor to the binding of lysozyme in a manner that interfered with its enzymatic activity or assay. Other investigations have indicated that isozymes of lysozyme are present in ruminants and this study suggests that ruminants have only low levels of the isozyme that is the major isozyme of lysozyme in non-ruminants.

Shark cartilage contains inhibitors of tumor angiogenesis

Shark cartilage contains a substance that strongly inhibits the growth of new blood vessels toward solid tumors, thereby restricting tumor growth. The abundance of this factor in shark cartilage, in contrast to cartilage from mammalian sources, may make sharks an ideal source of the inhibitor and may help to explain the rarity of neoplasms in these animals.

Stimulation of glycosaminoglycan sulfotransferase from chick embryo cartilage by basic proteins and polyamines

A soluble glycosaminoglycan sulfotransferase (3'-phosphoadenylylsulfate:chondroitin 4'-sulfotransferase, EC 2.8.2.5) from chick embryo cartilage has been prepared free from endogenous acceptor. The reaction with this enzyme preparation was stimulated by basic proteins and polyamines, the degree of stimulation being dependent on the chemical nature of both basic compounds and acceptor glycosaminoglycans. A maximum stimulation was obtained when protamine (basic compound) and chondroitin (acceptor) were involved in the reaction mixture at a molar ratio of protamine to repeating disaccharide units of chondroitin, 1:100. The stimulation of sulfotransferase activity by basic substances was much higher than that by Mn2+. However, increasing the Mn2+ concentration immediately reduced the stimulation by basic substances. The Km value for 3'-phosphoadenosine 5'-phosphosulfate of the sulfotransferase, when chondroitin was used as acceptor, was 1 . 10(-6) M in the presence of 25 microgram/ml protamine, compared to 2 . 10(-5) M in the absence of protamine. These observations indicate that the basic proteins and polyamines may interact with acceptor polysaccharide, thereby causing an increase in the affinity of the enzyme toward 3'-phosphoadenosine 5'-phosphosulfate.

Correlation of lysozyme activity with proteoglycan biosynthesis in epiphyseal cartilage

Pig epiphyseal cartilage (proximal ulna epiphysis) previously incubated into vitro in the presence of sodium [35S]sulfate or [3H]thymidine was either analyzed by autoradiography or separated into 9 morphologically defined consecutive layers and investigated for 35S-incorporation into the guanidinium chloride-extractable proteoglycans and for lysozyme activity. The lowest 35S incorporation and lysozyme activity were determined in the zone of resting cells, but there is a consecutive increase in the rate of proteoglycan synthesis and lysozyme activity toward the diaphyseal cartilage-bone junction, with the maximum at the lower columnar cell zone and a sharp reduction of both parameters at the hypertrophic zone. The maxima of 35S incorporation and [3H]thymidine incorporation do not coincide. The guanidinium chloride-soluble proteoglycans exhibit macromolecular polydispersity. Fractions excluded from as well as retarded by Sepharose 2B gel could be separated and were detected in all zones. The results indicate a correlation of proteoglycan biosynthesis and lysozyme activity in epiphyseal cartilage.