Purification and properties of extracellular chitinases from the parasitic fungus Isaria japonica.

Two chitinases (P-1 and P-2) induced with colloidal chitin were purified from the culture supernatant of Isaria japonica by chromatography on DEAE Bio-Gel, chromatofocusing and gel filtration with Superdex 75 pg. The enzymes were electrophoretically homogeneous and estimated to have a molecular mass of 43,273 (+/-5) for P-1 and 31,134 (+/-6) for P-2 by MALDI-MS. The optimum pH and temperature was 3.5-4.0 and 50 degrees C for P-1 and 4.0-4.5 and 40 degrees C for P-2. P-1 acted against chitosan 7B (degree of deacetylation, 65-74%) = glycol chitin > colloidal chitin = chitosan 10B (degree of deacetylation, above 99%) and P-2 against chitosan 7B > glycol chitin = chitosan 10B > colloidal chitin in order of activity. The products of hydrolysis of chitin and chitosan hexamer were analyzed by MALDI-MS. The products from the chitin hexamer obtained with P-1 were almost all dimers with only a small amount of trimer whereas those obtained with P-2 were mainly trimers with some dimer and tetramer. No hydrolysis of chitosan hexamer was observed. High homology in the amino-terminal sequence for chitinase P-1 was exhibited by chitinases from Trichoderma harzianum, Candida albicans and Saccharomyces cerevisiae in the range of 48-39%. The highest homology for Chitinase P-2 was shown by an endochitinase from Metarhizium anisopliae of 66%, while 44% homology was exhibited by chitinases of Leguminosae plants.

Overproduction of spinach betaine aldehyde dehydrogenase in Escherichia coli. Structural and functional properties of wild-type, mutants and E. coli enzymes.

Betaine aldehyde dehydrogenase (BADH) catalyzes the last step in the synthesis of the osmoprotectant glycine betaine from choline. Although betaine aldehyde has been thought to be a specific substrate for BADH, recent studies have shown that human and sugar beet BADHs also catalyze the oxidation of omega-aminoaldehydes. To characterize the kinetic and stability properties of spinach BADH, five kinds of expression vectors encoding full length, mature, E103Q, E103K, and chimera BADHs were constructed. These enzymes together with Escherichia coli BADH were expressed in E. coli and purified. The affinities for betaine aldehyde were similar in the spinach and E. coli BADHs, whereas those for omega-aminoaldehydes were higher in spinach BADH than in E. coli BADH. A chimera BADH in which part of the Rossmann type fold in the spinach BADH was replaced with that of E. coli BADH, showed properties which resembled spinach BADH more than E. coli BADH. The spinach E103K mutant was almost inactive, whereas the E103Q mutant showed a similar activity for the oxidation of betaine aldehyde to that of wild type BADH, but a lower affinity for omega-aminoaldehydes. All spinach BADHs were dimers whereas E. coli BADH was a tetramer. E. coli BADH was more stable at high temperature than spinach BADHs. The E103Q mutant was most labile to high temperature. These properties are discussed in relation to the structure of spinach BADH.

Catabolite inactivation of fructose 1,6-bisphosphatase and cytoplasmic malate dehydrogenase in yeast.

Catabolite inactivation of fructose 1,6-bisphosphatase and cytoplasmic malate dehydrogenase was studied using the protease-deficient and vacuole-defective yeast strain pep4-3. The catabolite inactivation of fructose 1,6-bisphosphatase in pep4-3 was found to have a normal first inactivation step but with a defective second proteolytic step. In contrast, catabolite inactivation of cytoplasmic malate dehydrogenase was normal in pep4-3. These results suggest that the proteolytic pathways utilized in the hydrolysis of the two enzymes may be different and that proteolysis of fructose 1,6-bisphosphatase may require functional vacuoles while proteolysis of cytoplasmic malate dehydrogenase may not.

Inorganic pyrophosphatase from pollen of Typha latifolia.

An inorganic pyrophosphatase was purified about 3,800-fold from the pollen of Typha latifolia by chromatography on DEAE-Sephadex A-50, isoelectric focusing and gel filtration through Sephadex G-75. The enzyme had an optimum pH between 8.5-9.5 and required Mg(2+). Since an excess of pyrophosphate over Mg(2+) inhibited the pyrophosphatase reaction, the actual substrate may have been an Mg-pyrophosphate complex. The enzyme degraded inorganic pyrophosphate specifically, showing a Km value of 7.6 × 10(-5) m. A possible role of pyrophosphatase was discussed in connection with starch-sucrose conversion.

Mapping of deoxydi- and trinucleotides liberated by the action of endonucleases from the silkworm and Aspergillis oryzae.

Both silkworm nuclease and nuclease O of Aspergillus oryzae mycelia hydrolyse DNA endolytically to di- and trinucleotides terminating in 5'-phosphate. These oligonucleotides were fractionated first be DEAE-cellulose chromatography with 7 M urea into the respective isoplithic groups and then analysed for the composition and isomerism: each group was labeled 5'-terminally by the [gamma-32P]ATP-polynucleotide kinase reaction and then electrophoresed monodimensionally for the dinucleotides and two-dimensionally for the di- and trinucleotides mixtures, respectively, followed by elution and digestion with snake venom exonuclease. Both nucleases gave rather similar simple maps in which all sixteen dinucleotides and almost all the possible trinucleotides were identified, indicating their random mode of actions.