A possible involvement of sulfhydryl groups in the conversion of lysine monooxygenase to an oxidase

Lysine monooxygenase catalyzes the oxygenation of lysine and arginine, and produces delta-amino-n-valeramide and gamma-guanidinobutyramide, respectively, concomitant with decarboxylation. In a preliminary communication, treatment of the native enzyme with p-chloromercuribenzoate was shown to inactivate the oxygenase and to induce an oxidase activity. The modified enzyme catalyzed predominantly the oxidative deamination of lysine and arginine resulting in the formation of the corresponding alpha-keto acid, ammonia, and hydrogen peroxide (YAMAUCHI, T., YAMAMOTO, S., and HAYAISHI, O.(1973) J. Biol. Chem. 2j8, 3750-3752). Paper electrophoresis, cellulose thin layer chromatography, and chemical degradation of the reaction products from lysine and arginine, provided further evidence for their identity with alpha-keto-epsilon-aminocaproate and alpha-keto-delta-guanidinovalerate, respectively. Further studies were carried out to establish the involvement of sulfhydryl groups in this conversion of the enzyme activities. Various sulfhydryl reagents including certain mercurials, alkylating, and oxidizing reagents, showed essentially identical effects on the enzyme. Dithiothreitol treatment reversed the conversion produced by various mercurials; the oxidase activity disappeared and the oxygenase activity was recovered. When p-chloromercuribenzoate was added to the enzyme and the increase in the absorbance at 250 nm was followed, 3.6 of the 6.5 half-cystine residues present per enzyme-bound FAD were readily titrated within 3 to 4 min. The inactivation of the oxygenase and the induction of the oxidase activity were almost maximal with 4 to 5 mol of p-chloromercuribenzoate/mol of enzyme, and these effects occurred within 3 to 4 min. These results together with other properties of the modified enzyme provided evidence for a possible involvement of these reactive sulfhydryl groups during the conversion of the oxygenase to an oxidase.

Immunologic significance of the mumps virus skin test in infants, children and adults

The biologic validity of cell-mediated immunity to mumps virus was evaluated in 395 children, adolescents and adults. The study protocol included the determination of cutaneous delayed hypersensitivity to viral and avian control antigens and in 79% of the subjects an essential double bleeding was performed before and after mumps virus skin test for assay of neutralizing antibody. Seven per cent of subjects expressed sufficient delayed hypersentitivity to the control antigen to erase an apparently positive mumps virus skin test. Anamnestic conversions from seronegativity to seropositivity, elicited by the mumps virus skin test, increased from 4% in children to 25% in adults, which suggests waning B-cell recognition of prior mumps virus infection in adults. Although pregnancy diminished the difference (p smaller than .001), adults showed greater cutaneous delayed hypersensitivity to mumps virus antigen than did children (p smaller than .001), suggesting that mumps virus reinfection or persistence induced the escalation of more sensitive T-cell recognition with increasing age. Humoral immunity, assessed by the double bleeding technique in the vast majority of individuals, rose form 16% (1-4 years), 45% (5-9 years) and 80% (10-14 years) to 94% in adolescents and adults. Ordinarily 75-95% in other age groups, the decline of correlation between mumps virus cellular and humoral immunity to 60% in school children may result from prior parainfluenza virus infection, inconsistent potency of the skin test antigen, concurrent immunosuppressive infection, and lagging induction of mumps virus cellular immunity in recently infected individuals. Immunologic study of a large colony of subhuman primates failed to establish an hierarchial antigenic interrelationship among mumps virus and two additional paramyxoviruses.

Alkylamine-dependent amino-acid oxidation by lysine monooxygenase--fragmented substrate of oxygenase

Lysine monooxygenase catalyzes the oxygenative decarboxylation of L-lysine and produces a corresponding acid amide. L-Alanine was inactive as substrate. However, when propylamine was present, oxidation, but not oxygenation, of alanine was demonstrated with the oxygenase. Alanine was converted to pyruvate, with the liberation of ammonia and hydrogen peroxide, but propylamine remained unchanged. Other alpha-monoamino acids were also oxidized in the presence of alkylamines with various carbon chain lengths. The highest oxidase activity was observed when the total chain length of both amino acid and amine was nearly identical with that of lysine. Available evidence indicates that the amine-dependent amino-acid oxidase activity is associated with the lysine oxygenase activity.

Spectrophotometric studies on lysine monooxygenase, a flavoprotein

The spectral changes of the enzyme-bound FAD were investigated in the anaerobic and aerobic reactions of lysine monooxygenase, a flavoprotein. Under anaerobic conditions, the enzyme FAD was fully reduced with lysine via a transient intermediate having a broad absorption band in the long wavelength region. This anaerobic species was presumably involved in the dehydrogenation of lysine leading to the formation of an α-keto acid. During the steady state of the aerobic reaction, a separate spectral species with a long wavelength absorption was observed. Both lysine and oxygen were required for its appearance. Kinetic evidence supports the intermediacy of this species in the oxygenation of lysine to an acid amide.