Biochimica et Biophysica Acta (BBA) - Specialized Section on Enzymological Subjects最新文献

• 1.

  1. The interaction of various penicillinases (penicillin amidohydrolase, EC 3.5.2.6) with methicillin and oxacillin has been studied.

• 2.

  2. The K_m values have been compared and found to reflect the phylogenetic and serological relationship of the penicillinases.

• 3.

  3. Methicillin and oxacillin accelerate the inactivation of penicillinases by heat and by urea, and expose groups sensitive to iodine and to p-chloromercuribenzoate (p-hydroxymercuribenzoate).

• 4.

  4. The response of penicillinases from different sources to various concentrations of these analogs has been compared.

• 5.

  5. The patterns of response are characteristic of the source of penicillinase, and essentially independent of the structure of the analog.

• 6.

  6. A comparison of these patterns brings out subtle differences in the tertiary structure of the active sites of closely related enzymes.

• 7.

  7. The sensitivity of such analysis is illustrated by the difference in reponse patterns of enzymically and serologically indistinguishable induced and constitutive enzyme preparations.

The electron-transfer reactions associated with acyl-CoA dehydrogenase (acyl-CoA: DPN⁺ oxidoreductase), hydrogenase (EC 1.98.1.1) and lactic dehydrogenase (dl-lactate: (acceptor) oxidoreductase) in the rumen microorganism Peptostreptococcus elsdenii were studied and a pathway of electron transport in the organism proposed. Acyl-CoA dehydrogenase was resolved into dehydrogenase and an associated electron-transport protein (Fraction II) which accepts electrons from DPNH and passes them to the dehydrogenase. The two components were purified and partially characterized. Data indicating the presence of a ferredoxin-linked DPN⁺ reductase (reduced ferredoxin: DPN⁺ oxidoreductase) are presented.

• 1.

  1. The biosynthesis of adenosine diphosphate glucose and adenosine diphosphate mannose from adenosine triphosphate and respectively glucose 1-phosphate and mannose 1-phosphate has been observed in extracts from mammalian tissues. The reaction is reversible in the presence of the nucleoside diphosphate sugar and pyrophosphate.

• 2.

  2. Two different enzymes are probably responsible for the reactions with either adenosine diphosphate glucose or adenosine diphosphate mannose.

• 3.

  3. Adenosine diphosphate mannose may be synthesized by the same enzyme which catalyzes the biosynthesis of guanosine diphosphate mannose and inosine diphosphate mannose.

• 4.

  4. Evidence is presented that adenosine diphosphate glucose pyrophosphorylase (ATP: α-d-glucose-1-phosphate adenylyltransferase) may be a specific enzyme.

• 5.

  5. The relative levels of nucleoside diphosphate hexose pyrophosphorylases have been measured in different extracts from mammals, plants or yeast. From these data the possible significance of adenosine diphosphate glucose pyrophosphorylase in mammals is discussed.

The Saccharomyces haploid stock 8050B is a galactose fermenter which was found by chromatography on CM-cellulose and electrophoresis on agar gel to contain a major and a minor form of phosphoglucomutase (d-glucose-1,6-diphosphate:d-glucose-1-phosphate phosphotransferase, EC 2.7.5.1). Mutations in the Ga₅ locus of this stock reduced the phosphoglucomutase activity in extracts 4–5-fold and rendered the cells unable to ferment galactose. The reduction in enzyme activity of the mutants was shown to be due to the fact that the synthesis of the major phosphoglucomutase component was blocked, although the minor component was not affected. The two phosphoglucomutases are probably the products of different genes.

• 1.

  (1) A trypsinogen-activating proteolytic enzyme (peptidase A) has been isolated from the growth medium of Penicillium janthinellum and purified about 60-fold; it is homogeneous in the ultra-centrifuge and on electrophoresis. Its molecular weight is 32 000.

• 2.

  (2) The enzyme has the following amino acid composition: Lys₅, His₃, Asp₃₆, Thr₂₈, Ser₄₂, Glu₂₈, Pro₁₂, Gly₃₉, Ala₂₃, Val₂₂, Ileu_12.5, Leu₂₀, Tyr₁₄, Phe₁₉, Try_4–5. It does not contain arginine, methione and half-crystine.

• 3.

  (3) The system peptidase A-trypsinogen follows Michealis-Menten kinetics, giving K_m = (7.6±2) · 10⁻⁶ M (at 0°, pH 3.4).

• 4.

  (4) Peptidase A apparently does not act on small peptides, but readily degrades apoferritin and bovine serum albumin. About 15% of the peptide bonds in bovine serum albumin are hydrolysed.