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Pleurotus ostreatus mycelium was grown in the presence of tobacco and wheat straw juices, ground wheat straw and acid-precipitable polymeric lignin with the aim of increasing the production of extracellular enzymes potentially implicated in lignin degradation. The highest production of diphenol oxidases was obtained when culture broths were supplemented with solid straw or tobacco juice; cellulase and veratryl alcohol oxidase were produced in detectable amounts in the presence of solid straw and in the absence of any inducer, respectively. No lignin peroxidase was found under any growth condition. Chromatographic fractionation of extracellular proteins and kinetic analysis of partially purified fractions showed that, in the absence of inducers, o -, p - and m -diphenol oxidases could be detected in column eluates, whereas all the inducers tested increased selectively the production of o -diphenol oxidases.

We have designed and implemented on a personal computer a program for identifying and quantifying the fragments present in a peptide mixture obtained by hydrolysing a polypeptide of known sequence using digesting agents. The qualitative data utilized by the main algorithm consist of the target sequence of the intact molecule and the amino acid residues identified at each step of the automatic sequence analysis of the unfractionated digestion mixture. In this way, the sequence of each fragment present in the mixture is quickly reconstructed. Furthermore, if the quantitative data of the amino acid residues identified at each step of the sequence analysis are utilized, the program will correlate the sequence of each fragment to its amount. We furnish an example of the application intended for the rapid identification and characterization of the extracellular proteinases produced by a basidiomycete fungus, utilizing the bovine insulin beta-chain as target substrate. A variety of uses for the method are discussed.

A protein inhibitor which is active against both exogenous and endogenous trypsin has been purified from wheat endosperm. The inhibitor is a single-chain protein of M r 8500 and isoelectric point 8.7. It contains 10 half-cystine residues per mol, all of them linked in disulphide bridges. The N -terminal sequence, 25 residues long, has been determined. The inhibitor is very active against bovine, porcine, cod and wheat trypsin, and inactive against animal chymotrypsin and bacterial subtilisin. The inhibitor binds bovine trypsin with a 1:1 molar stoichiometry.

Cytosolic aspartate aminotransferase (EC 2.6.1.1) from ox heart has been fully characterized; the most significant results have been reviewed. An investigation is now in progress to establish structural and evolutionary relationships between this enzyme and the homologous one from pig heart, whose complete primary structure has been reported. A more complete picture from an evolutionary point of view should also arise from a comparison of the mitochondrial enzymes. In fact the primary structure of the mitochondrial porcine enzyme has been reported. Structural investigations on cytosolic and mitochondrial chicken aspartate aminotransferases are being pursued. Therefore we have undertaken the purification and characterization of mitochondrial bovine aspartate aminotransferase. Preliminary sequence and crystallographic data are reported here.

Reactivity of sulphydryl groups of cytosolic and mitochondrial aspartate aminotransferases from ox heart has been studied. A total of 5 and 7 cysteine residues per monomer are present in cAATo and mAATo, respectively. In native conditions only a single sulphydryl group can be titrated by Nbs2 while the catalytic activity remains unchanged, however in the mitochondrial isozyme the reactivity depends on the functional state of the enzyme. Reactivity toward NEM reveals the existence of a syncatalytic sulphydryl group in the cytosolic isozyme. Titration of cAATo with pMB at pH 8 and pH 5 confirms the existence of two exposed sulphydryl groups with a different reactivity. The results compared with those reported on the corresponding isozymes from pig and chicken heart show that syncatalytic sulphydryl groups are of general occurrence in these enzymes.