ENZYMATIC ENHANCEMENT OF INFECTIVITY OF REOVIRUS

Spendlove, R. S. (California State Department of Public Health, Berkeley), and F. L. Schaffer. Enzymatic enhancement of infectivity of reovirus. J. Bacteriol. 89:597-602. 1965.-Enhancement of infectivity by chymotrypsin treatment has been demonstrated with all three types of reovirus, although not in all viral preparations. Enzyme treatment did not produce a simultaneous increase in the hemagglutinating activity of reovirus type 1 (the only type tested). The infectivity of reovirus type 1 (Lang strain) was increased by treatment with chymotrypsin, trypsin, papain, and a filtrate from a culture of a Pseudomonas sp. but not by treatment with pepsin. Sedimentation experiments showed that the property of enhanceability was closely associated with the virus particles themselves. Results of studies involving various sequential treatments with chymotrypsin, and with heat in the presence or absence of 2 m MgCl(2), were compatible with the interpretation that inhibited virus is resistant to exposure to a temperature of 56 C in the absence of MgCl(2), whereas activated virus is thermolabile. Activation of reovirus infectivity by heat in the presence of MgCl(2) and by chymotrypsin was not additive.

A STUDY OF SOME THIOL ESTER HYDROLYSES AS MODELS FOR THE DEACYLATION STEP OF PAPAIN-CATALYSED HYDROLYSES

1. The self-catalysed hydrolyses of the thiol esters, S-hippurylthioglycollic acid and S-ethyl monothiolsuccinate, have been shown to be slower than the deacylation step for the papain-catalysed hydrolysis of hippuric esters, by a factor approx. 10(5). This difference in rate constants largely reflects a difference in activation energy, which together with other evidence drawn from the literature make it unlikely that a carboxylate ion could be the nucleophile responsible for the deacylation of acyl-papain. 2. The imidazole-catalysed hydrolysis of S-hippurylthioglycollic acid and ethyl thiolacetate have activation energies similar to that for the deacylation step in papain-catalysed hydrolyses. This, together with other evidence drawn from the literature, suggests that the imidazole of a histidine residue is the nucleophile responsible for the deacylation of acyl-papain.

OXYGEN-STABLE HEMOLYSINS OF GROUP A STREPTOCOCCI. 3. THE RELATIONSHIP OF THE CELL-BOUND HOMOLYSIN TO STREPTOLYSIN S

The relationship of the streptococcal hemolysin which is recognized on incubation of RBC with streptococcal cells (cell-bound hemolysin, CBH), to RNA hemolysin, a representative of oxygen-stable hemolysin (streptolysin S) has been studied. A number of similarities have been found in the conditions for optimal production of each of these hemolysins, a requirement for cysteine, Mg(++), and glucose; maximal production by streptococci in the stationary phase; similar curves of pH-dependence. In both systems, the production of hemolysin was inhibited by certain antibiotics, by ultraviolet irradiation, and by sonic disruption and was absent in the same streptococcal mutant strain. The hemolytic activity of both systems was inhibited by lecithin, trypan blue, and papain. Similarities were also found in relative susceptibilities to the two hemolytic systems of erythrocytes of a number of animal species. These data support a suggestion advanced in an earlier study that a streptococcal hemolytic moiety, which can be induced by, and carried on, a number of diverse agents to comprise the group of oxygen-stable hemolysins, serves, in its original attachment to a component of the streptococcal cell, to produce the hemolytic effect recognized as the cell-bound hemolysin.

EVIDENCE FOR AN EXOCELLULAR SITE FOR THE ACID PHOSPHATASE OF SACCHAROMYCES MELLIS

Weimberg, Ralph (Northern Regional Research Laboratory, Peoria, Ill.), and William L. Orton. Evidence for an exocellular site for the acid phosphatase of Saccharomyces mellis. J. Bacteriol. 88:1743-1754. 1964.-Evidence is presented which demonstrates an exocellular location for acid phosphatase in Saccharomyces mellis. Derepressed intact cells exhibit acid phosphatase activity. The properties of the system are similar to those shown by the enzyme in cell-free extracts. There is no increase in total activity when cell-free extracts are prepared. Enzymatically active cell walls were prepared by leaching acetone-dried cells of this yeast in dilute acetate buffer (pH 6.5) plus beta-mercaptoethanol. The insoluble residue, consisting mainly of cell-wall material and containing the phosphatase, was treated with a variety of hydrolytic enzymes and other chemicals. Only papain and crude snail gut extracts dissociated the enzyme from the particulate fraction in nearly quantitative amounts. The mechanism of release by these two enzymes probably differs. Of all enzymes tested, only the snail gut extract digested the cell walls. By dividing the procedure for making protoplasts of S. mellis into two steps, acid phosphatase may be dissociated from resting cells and recovered as an active soluble enzyme. The first step is to pretreat the cells with a thiol reagent. The second step is to digest the cell wall by enzymes present in crude snail gut extracts. Arsenite must be included in the second step to protect the phosphatase from inactivation. The phosphatase is quantitatively released before the cell becomes osmotically fragile.

THE CATABOLISM OF HOMOLOGOUS AND HETEROLOGOUS 7S GAMMA GLOBULIN FRAGMENTS

The catabolism of homologous and heterologous 7S gamma globulin fragments obtained by pepsin and papain digestion was studied in rabbits, guinea pigs, and mice. The elimination from the circulation of I* labeled gamma globulin fragments was followed and the urinary excretion of the total and protein-bound I* activity determined. Evidence is presented that the molecular structure responsible for the catabolism of 7S gamma globulin is located in papain fragment III. The elimination of papain fragment III was slow and closely related to the intact gamma globulin, whereas the pepsin fragment and papain fragments I and II were rapidly eliminated and catabolized in all species examined. Prolonged incubation with cysteine altered papain fragment III as shown by a rapid catabolism of a large portion of incubated fragment III within 24 hours after injection. Small amounts of intact RGG and RGG papain fragment III were excreted as protein-bound I* activity in the urine. On the other hand, large amounts of the pepsin fragment and papain fragments I and II of RGG were excreted as protein-bound I* activity in the urine. The possibility of a molecular structure present in papain fragment III, which may be responsible for tubular reabsorption in the kidney, is discussed. The rate of urinary excretion of fragments obtained from RGG was different from that of fragments obtained from gamma globulin of several other species. In general, small amounts of the pepsin fragment and papain fragment III obtained from gamma globulin other than RGG were excreted as protein-bound I* activity. The amounts of fragment I* excreted as protein-bound I* activity depended on the species in which it was injected, as well as the source of the gamma globulin. The rapid catabolism of the pepsin fragment and papain fragments I or II which bear antibody-combining sites suggest that their use for the prophylactic treatment of tetanus and diphtheria in man is limited.

CORROBORATION OF RECENT MODELS OF THE GAMMA-G IMMUNOGLOBULIN MOLECULE

The relationships between the polypeptide chains of γG immunoglobulin and fragments of the molecule produced by papain and pepsin have been investigated. Specific procedures were employed including peptide mapping of tryptic hydrolysates and analysis of molecules reconstituted from chains labeled with different iodine isotopes. By these means, the Fab fragment was shown unequivocally to consist of the light chain and a portion of the heavy chain, the Fd fragment. The Fc fragment was found to be comprised of the residual portions of the heavy chain. These findings support the gross arrangement of chains embodied in recent models of the γG immunoglobulin molecule. The present studies have also provided additional information on the susceptibility of γG immunoglobulin to proteolytic cleavage. It was found that the portion of heavy chains corresponding to the Fd fragment was extensively cleaved by papain.

A NEW CLASS OF HUMAN IMMUNOGLOBULINS. I. A UNIQUE MYELOMA PROTEIN

The unique myeloma protein from S. J., a patient with multiple myeloma, was isolated and characterized. It resembled other myeloma proteins in many respects. The S. J. myeloma protein migrated in a distinct peak in the slow β-globulin region on zone electrophoresis, appeared as a single band on starch gel electrophoresis, and sedimented at 7.04S in the ultracentrifuge. Papain and cysteine treatment produced Fc (fast) and Fab (slow) fragments. Reduction and alkylation of the myeloma protein produced heavy and light chains in a ratio of approximately 3:1. The S. J. myeloma protein had type L (type II) light chains. These were antigenically similar to the Bence Jones protein also found in this patient. The S. J. myeloma protein was unique in the properties of its heavy chains. The myeloma protein (and its heavy chains and Fc pieces) did not contain antigenic determinants specific for IgG, IgA, or IgM. The myeloma protein (and its heavy chains), however, did contain antigenic determinants which are characteristic of a new class of immunoglobulin. The S. J. myeloma protein was unusual also in its effect on the metabolism of normal IgG and in the electrophoretic mobility of the Fc fragment produced by papain digestion. No evidence was obtained to indicate that the entire heavy polypeptide of the S. J. protein was a grossly abnormal product of malignant cell metabolism. The unique properties of the S. J. myeloma protein (and its heavy chains) are believed to represent, in large measure, properties to be found in a small part of the normal immunoglobulin population.

STRUCTURAL STUDIES OF HUMAN 7S GAMMA-GLOBULIN (G IMMUNOGLOBULIN). FURTHER OBSERVATIONS OF A NATURALLY OCCURRING PROTEIN RELATED TO THE CRYSTALLIZABLE (FAST) FRAGMENT

1. Detailed physical, chemical, and immunologic studies of a protein closely related to the Fc fragment and heavy chain of G immunoglobulin (IgG), and elaborated by a subject with a lymphoproliferative disorder are presented. 2. The protein, which has a molecular weight of 51,000, was cleaved into two half molecules by reduction and alkylation. 3. The protein has few if any of the antigenic determinants of the antigen-binding (Fab) papain fragment of IgG, and has a striking similarity in its antigenic properties to the Fc fragment. 4. Fingerprint patterns resemble those of the crystallizable (Fc) fragment, and lack several peptides found in the heavy chain. 5. These findings suggest that the Fc fragment may be a real structural unit of IgG, and raise the possibility of the existence of three different types of polypeptide chains in G immunoglobulin.

THE EFFECT OF PROTEOLYTIC ENZYMES ON E. COLI PHAGES AND ON NATIVE PROTEINS

Lambda coli phage is not inactivated by chymotrypsin, trypsin, or ficin. T(2) phage is slowly inactivated by high concentrations of (alpha-, beta-, gamma-, or Delta-chymotrypsin, but not by trypsin or ficin. P(1) phage is slowly inactivated by alpha-, beta-, or gamma-chymotrypsin, or ficin, more rapidly by Delta-chymotrypsin, and much more rapidly by trypsin. Crystalline egg albumin, crystalline serum albumin, E. coli nucleoprotein, and yeast nucleoprotein are hydrolyzed slowly by alpha-chymotrypsin. Yeast nucleoprotein, like P(1) phage, is hydrolyzed more rapidly by Delta-chymotrypsin than by alpha-chymotrypsin, but not by trypsin or ficin. Neither phages nor native proteins were attacked by papain, carboxypeptidase, deoxyribonuclease, or ribonuclease.

DIFFERENCES IN THE ELECTROPHORETIC MOBILITIES OF GUINEA PIG 7S ANTIBODIES OF DIFFERENT SPECIFICITIES

The electrophoretic mobilities of guinea pig gamma(1) and gamma(2) antibodies bearing different specificities were compared in agar gel at pH 8.2. Specifically purified antibodies bearing the same immunological specificity showed the same electrophoretic mobility, but significant differences in mobility were observed when antibodies with certain selected different specificities were compared. The specificity of the carrier protein appeared not to affect the mobilities of antihapten antibodies. Differences in mobility have also been shown between gamma(1) antihapten antibodies produced by individual guinea pigs immunized concomitantly with 2,4-dinitrophenyl bovine gamma globulin and arsanilic acid azo guinea pig albumin. The differences in the net electrophoretic charge between antibodies with different specificities roughly paralleled that of their S fragments produced by papain digestion.

THE EFFECTS OF PAPAIN, VITAMIN A, AND CORTISONE ON CARTILAGE MATRIX IN VIVO

The extreme and, apparently, selective vulnerability of chondromucoprotein in cartilage matrix to the action of proteolytic enzymes in vivo provides a useful model for studying factors involved in the transport, inhibition, and activation of a protease, papain, in the blood and tissues. The lysis of cartilage matrix which occurs in hypervitaminosis A is the result of release, probably from chondrocytes, of cathepsins normally contained within lysosomes. Cortisone possesses two properties which are not only of importance for this experimental model but also may have more general bearing on the physiological functions of this hormone with respect to connective tissue. One property is to prevent the resynthesis or deposition of chondroitin sulfate in cartilage matrix, after depletion of the latter. The other, which may be relevant to the "anti-inflammatory" actions of cortisone, is to increase the stability of lysosomes and prevent release of the acid hydrolytic enzymes contained in these organelles.

INDIVIDUAL ANTIGENIC SPECIFICITY OF MYELOMA PROTEINS. CHARACTERISTICS AND LOCALIZATION TO SUBUNITS

The specific antigenic structure of individual myeloma proteins was investigated for the presence of similar antigenic determinants in pooled gamma-globulin and for the localization of these determinants on the gamma-globulin molecules. Quantitative precipitin analyses demonstrated that in most instances absorption of antisera specific for an individual myeloma protein with large amounts of gamma-globulin markedly reduced or completely removed the reactivity of the antiserum for the homologous myeloma protein. In only one instance did strong specificity remain after absorption with 100 mg of Fr II per cc of antiserum. The antigenic determinants responsible for the individual specificity were localized in all cases studied solely to the Fab fragment produced by papain digestion. After reductive cleavage, three patterns of localization were observed. Individual specificity could be localized either to; (a) isolated heavy chains, (b) isolated light chains, (c) antigenic determinants present only when light and heavy chains were recombined. After immunization with whole myeloma proteins, individual specificity was localized in part at least to the isolated heavy chain in four of six proteins studied. It was localized to the light chains in three of five type L proteins but in none of six type K proteins. In the instances where individual specificity of the myeloma protein was present on the light chains, it was shown that the Bence Jones protein from the same patient also contained the individual specificity. Immunization with isolated heavy or light chains furnished further evidence for the individual specificity of both types of chains. These studies on myeloma proteins furnished evidence concerning the portions of the gamma-globulin molecule subject to individual antigenic variation. The light chains, particularly the L type and the Fd portion of the heavy chains were primarily involved. Evidence for the importance of the quaternary structure was also obtained from the necessity in some instances for light and heavy chains to be associated in order for individual specificity to be observed. The Fc fragment of the heavy chains on the other hand showed very limited variation which was related to subgroup specificity.

PAPAIN-CATALYSED HYDROLYSIS OF SOME HIPPURIC ESTERS. A NEW MECHANISM FOR PAPAIN-CATALYSED HYDROLYSIS

1. The Michaelis-Menten parameters for the papain-catalysed hydrolysis of a number of alkyl, aryl and alkyl-thiol esters of hippuric acid have been determined. 2. For all the aryl esters and most of the alkyl esters studied, the catalytic constant, k(0), is 2-3sec.(-1) and most probably represents deacylation of the common intermediate, hippuryl-papain. 3. Two alkyl esters and hippurylamide, however, have catalytic rate constants, k(0), less than 2-3sec.(-1). It is possible to interpret all the available kinetic data in terms of a three-step mechanism in which an enzyme-substrate complex is first formed, followed by acylation of the enzyme through an essential thiol group, followed by deacylation of the acyl-enzyme. 4. The logarithm of the ratio of the Michaelis-Menten parameters, which reflect the acylation rate constant, for four aryl esters of hippuric acid studied give a linear Hammett plot against the substituent constant, sigma. Arguments are presented that indicate acid as well as nucleophilic catalysis in the acylation process and that the most likely proton donor is an imidazolium ion. 5. It is suggested that this imidazolium ion is part of the same histidine residue that has been tentatively implicated in the deacylation process (Lowe & Williams, 1965b). 6. A new mechanism is proposed for the papain-catalysed hydrolysis of N-acyl-alpha-amino acid derivatives.

DIRECT EVIDENCE FOR AN ACYLATED THIOL AS AN INTERMEDIATE IN PAPAIN- AND FICIN-CATALYSED HYDROLYSES

1. Methyl thionohippurate was prepared and shown to be a specific substrate for both papain and ficin. 2. The ultraviolet-absorption properties of the acyl-enzyme intermediate for both papain and ficin with methyl thionohippurate was that expected of an acyl-thiol. The possibility that other functional groups present in papain or ficin might be the site of acylation has been excluded. 3. The change in extinction at the absorption maximum with time was as expected for the acyl-enzyme on the basis of the known Michaelis-Menten parameters for methyl thionohippurate. 4. The variation of extinction with initial substrate concentration for both papain and ficin was that expected from the Michaelis-Menten parameters. 5. The extinction of the absorption maximum of the thionohippuryl-enzyme intermediate was suppressed by the addition of methyl hippurate to the extent predicted from the Michaelis-Menten parameters. 6. The decay of the extinction for the acyl-enzyme was arrested by adjusting the pH of the solution to 2.5. 7. These experiments provide compelling evidence that the acylation by substrate of both papain and ficin takes place through a thiol residue.