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PubMed1965

THE CELL-BOUND ALPHA-AMYLASES OF STREPTOCOCCUS BOVIS.

1. The cell-bound alpha-amylase of Streptococcus bovis has been isolated from other carbohydrases in the cell extract by chromatography on DEAE-cellulose. The enzyme has been compared with the extracellular alpha-amylase produced by this organism. 2. The two amylases had similar action patterns on amylose, the main product being maltotriose with smaller amounts of maltose and a little glucose. 3. The cell-bound amylase hydrolysed maltopentaose and maltohexaose at a similar rate to the hydrolysis of amylose. Maltotetraose was hydrolysed six times more slowly, and maltotriose 280 times more slowly, than amylose. 4. Studies with end-labelled maltodextrins revealed that the cell-bound alpha-amylase preferentially hydrolysed the third linkage from the non-reducing end, liberating maltotriose. The linkage at the reducing end of maltotriose was more easily hydrolysed than the other. 5. Egg-white lysozyme and the extracellular enzymes of Streptomyces albus lysed the cell walls of Streptococcus bovis, releasing amylase into the medium. In the presence of 0.6 m-sucrose 10% of the maximal amylase activity was released by lysozyme. Suspension of the spheroplasts in dilute buffer caused the rupture of the cytoplasmic membrane and the liberation of amylase. 6. A sensitive method for determining the ability of amylases to degrade starch granules is described.

Amylases↗
PubMed1965

REMOVAL OF THE N-TERMINAL RESIDUE OF A PROTEIN AFTER TRANSAMINATION.

1. Pseudomonas cytochrome c-551 was modified by treatment at 20 degrees with glyoxylate in the presence of pyridine and cupric sulphate. The change in its chromatographic properties was consistent with conversion of its N-terminal residue into an oxo acyl residue by transamination. 2. The product underwent further modification on treatment with o-phenylenediamine or 4-methylphenylene-1,2-diamine in strong acetate buffer at 37 degrees . The final product had chromatographic properties and the N-terminal residue consistent with its differing from the native cytochrome solely in the absence of the original terminal residue. 3. The nature of analogous reactions supports these interpretations of the modifications. 4. These two treatments provide a method for specific removal of the N-terminal residue of a protein. 5. The intermediate and final products were oxidized by cytochrome oxidase at about the same rate as the original cytochrome.

Acetates↗
PubMed1965

RAT-KIDNEY LYSOSOMES: ISOLATION AND PROPERTIES.

1. The activities of lysosomal enzymes in the cortexes and medullas and the principal subcellular fractions of rat kidney were measured. 2. A method is described for the isolation of rat-kidney lysosomes and a detailed analysis of the enzymic composition of the lysosomes is reported. Enzyme analysis of the other principal subcellular fractions is included for comparison. 3. Studies of the distribution of alpha-glucosidase showed that the lysosomal fraction contained only 10% of the total enzyme activity. The microsomal fraction contained most of the particulate alpha-glucosidase. Lysozyme was concentrated mainly in the lysosomal fraction with only small amounts present in the microsomal fraction. Lysosomal alpha-glucosidase had optimum pH5 whereas the microsomal form had optimum pH6. Both lysosomal and microsomal lysozyme had optimum pH6.2. 4. The stability of lysosomal suspensions was studied. Incubation at 37 degrees and pH7 resulted in first an increased availability of enzymes without parallel release of enzyme. This was followed by a second stage during which the availability of enzymes was closely related to the release of enzymes. These changes were closely paralleled by changes in light-scattering properties of lysosomes. 5. The latent nature of the alpha-glucosidase and lysozyme of intact kidney lysosomes was demonstrated by their graded and parallel release with other typical lysosomal enzymes. 6. Isolated lysosomes were unstable at pH values lower than 5, most stable at pH6-7 and less stable at pH 8-9. Lysosomes were not disrupted when the osmolarity of the suspending medium was decreased from 0.6m to 0.25m. 7. The discussion compares the properties and composition of kidney lysosomes, liver lysosomes and the granules of macrophages. 8. The possible origin of the lysozyme in kidney lysosomes by reabsorption of the lysozyme in blood is discussed.

Acid Phosphatase↗
PubMed1965

THE ACTION OF HOT FORMAMIDE ON BACTERIAL CELL WALLS.

1. The cell walls of Corynebacterium tritici contain much carbohydrate and their mucopeptide contains diaminobutyric acid instead of lysine or diaminopimelic acid. They are resistant to lysozyme. 2. The residue after extraction with hot formamide contains only about 10% less carbohydrate but is attacked by lysozyme. Lysozyme also slowly attacks cell walls treated with fluorodinitrobenzene and more rapidly cell walls that have been N-acetylated. 3. All these processes block the free gamma-amino groups of diaminobutyric acid present in the untreated cell wall. Hot formamide introduces formyl groups, as shown by its ability to make formylglycine and diformyl-lysine under the same conditions. 4. N-Formyl groups are also introduced into the cell walls of Micrococcus lysodeikticus by hot formamide, but this change increases only slightly their already great sensitivity to lysozyme. N-Acetylation also increases sensitivity to lysozyme.

Bacillus megaterium↗
PubMed1964

OBSERVATIONS ON THE FINE STRUCTURE OF SPHEROPLASTS OF RHODOSPIRILLUM RUBRUM.

Spheroplasts of the photosynthetic bacterium Rhodospirillum rubrum were prepared from cultures grown in either the presence or absence of light. Cells were converted into spheroplasts by using lysozyme and Versene and fixed in a sucrose-veronal-acetate buffer mixture containing osmium tetroxide. Some preparations were shadow-cast and examined whole; others were embedded in Epon 812 and sectioned. The action of lysozyme and Versene appears to result in removal of the cell wall in strips. The relationship of the chromatophores to the cytoplasmic membrane is readily visualized in sections of broken spheroplasts, and in areas the chromatophores are seen to be continuous with the membrane. In all preparations examined, no definite connections between individual chromatophores were observed. In some cells large spherical granules were evident which either possessed or lacked a clearly visible limiting membrane. On serial sectioning, all granules appeared bounded by a single membrane 40 A wide. The granule membrane was well defined only if the section came from the center of the granule. Sections at other levels showed either a diffuse membrane or no membrane at all. The reasons for this are discussed.

Cell Biology↗
PubMed1964

ELECTRON MICROSCOPIC LOCALIZATION OF ACID PHOSPHATASE AND THIAMINE PYROPHOSPHATASE ACTIVITY IN HYPOTHALAMIC NEUROSECRETORY CELLS OF THE RAT.

Supraoptic nuclei in the hypothalamus of rats were fixed for the electron microscope by vascular perfusion with solutions of glutaraldehyde followed by post fixation with osmium tetroxide. Cytochemical methods for detection of acid phosphatase and thiamine pyrophosphatase activity have been applied to glutaraldehyde-fixed frozen sections containing the neurosecretory cells. The enzyme activities have been localized to certain Golgi cisternae. Acid phosphatase activity is present in the large (0.4 micro to 1.0 micro) granules or dense bodies which are surrounded by a single limiting membrane; both features characterize these structures as lysosomes. Smaller (0.1 micro) granules also present in the perikarya are generally unreactive towards enzyme activity and resemble in form the neurosecretory granules in the neurohypophysis.

Acid Phosphatase↗
PubMed1963

Accessory plasma factors involved in the bactericidal test for type-specific antibody to group A Streptococci. II. Human plasma cofactor (s) enhancing opsonization of encapsulated organisms.

A study was made of the nature of the thermolabile plasma factors in human blood which promote the phagocytosis of Group A streptococci in vitro in the presence of optimal amounts of type-specific M antibody. The plasmas of individuals with strong opsonic activity (normal) were compared with those of some individuals whose opsonic activity was consistently weak (deficient). A general relationship was established between encapsulation of streptococci and the opsonic requirement for thermolabile plasma factor(s). Marked differences in phagocytosis of Group A organisms by human bloods were demonstrated with encapsulated strains only. Human bloods deficient in the cofactor required for opsonization of encapsulated streptococci (coopsonin) showed a normal rate of phagocytosis against all other organisms and particles studied. Furthermore, coopsonin-deficient bloods contained normal levels of four components of complement, of properdin, of lysozyme, and of direct bactericidal activity against several species of Gram-negative organisms and of E. coli bacteriophage. The independence of the streptococcal coopsonin from complement was also demonstrated by absorption of plasma with bentonite and with zymosan. Under appropriate conditions, the coopsonin was reduced without significant loss of complement. The data support the concept that the capsule of the streptococcus imposes an opsonic requirement for a plasma factor(s) which is present in varying amounts in human bloods and which appears to be independent of the complement system. The possibility that it is accessory to the latter components has not been excluded.

Antibodies↗
PubMed1963

THE PARTICULATE HYDROLASES OF MACROPHAGES. II. BIOCHEMICAL AND MORPHOLOGICAL RESPONSE TO PARTICLE INGESTION.

The influence of phagocytosis on the morphological and biochemical properties of macrophage hydrolase-containing granules has been studied in vitro. Following the uptake of large numbers of heat-killed bacteria, an intracellular rearrangement of hydrolytic enzymes occurred. This was associated with the solubilization of 50 to 60 per cent of the total cell content of acid phosphatase, cathepsin, lysozyme, beta glucuronidase, acid ribonuclease, and acid desoxyribonuclease and with a corresponding decrease in granule-bound enzyme. With more prolonged incubation the majority of the soluble intracellular pool of acid ribonuclease and lysozyme was lost to the extracellular medium. No change in the total content of any of the hydrolases was noted during 180 minutes of incubation in vitro. The morphological fate of the granules was studied by a histochemical method for acid phosphatase. After the phagocytosis of yeast cell walls there was a disappearance of acid phosphatase-positive granules and an accumulation of reaction product about the ingested particle. Experiments employing macrophages which were supravitally stained with neutral red also demonstrated the loss of neutral red-positive granules and the accumulation of the dye about the yeast cell walls. These results strongly suggest that lysis of macrophage granules occurs following phagocytosis and that a portion of the granule contents are then resegregated within the newly formed phagocytic vacuole.

Acid Phosphatase↗