Calpains are neutral Ca2+-dependent cysteine proteases. In this study, we utilized casein zymography to detect such a proteolytic activity in Drosophila melanogaster extracts throughout the life of this organism. One calpain-like activity that was sensitive to the general cysteine protease inhibitors, E64 and calpain inhibitor I, but insensitive to the human calpain-specific inhibitor, calpastatin, is demonstrated. The relevance of this finding is discussed with respect to the absence of a corresponding Drosophila gene, homologous to the vertebrate calpastatin genes, as concluded from our unsuccessful attempts to clone such a gene and our Blast searches using the FlyBase. The mechanisms of Drosophila calpain regulation require further investigation. However, we suggest that single chain, non-heterodimeric calpains may be insensitive to calpastatin and that Drosophila cystatin-like molecules may play a role in negatively regulating Drosophila calpain.

DNA polymerase-α from the cytosol of regenerating rat liver has been highly purified by a procedure which includes affinity chromatography. The purified enzyme sediments at 7.4 S in high ionic strength and at 9–10 S in low ionic strength, i.e. under in vitro polymerization conditions. This enzyme has all the properties of the other mammalian DNA polymerases-α: sensitivity to sulfhydryl-blocking agents, to heparin, and to the level of salt in the assay, neutral pH optimum, use of ribonucleotide-initiated DNA templates, and inability to copy the ribostrand of hybrids. After chromatography on denatured DNA-cellulose, the α-polymerase is completely devoid of exo- and endonuclease activities. Template competition experiments indicate that the binding of the enzyme to the template can be distinguished from the polymerization itself and that the in vitro synthesis catalyzed by this α-polymerase is not distributive in a classical sense. These facts are discussed.

Two mutations affecting either the temperature sensitivity or the catalytic properties of the levansucrase of Bacillus subtilis Marburg were characterized. The relevant altered levansucrases were purified and their properties compared with those of the unmodified levansucrase. The results of this analysis and the genetic mapping of these mutations indicates that the structural gene of levansucrase is located in the sacB locus on the Bacillus subtilis chromosome between the cysB3 and hisA1 markers.

Pleiotropic mutations of the chromosome of Bacillus subtilis 168 affecting simultaneously the levels of extracellular levansucrase and proteolytic activities are described. These mutations have been mapped at the sacU locus identified by PBS 1 mediated transduction. Several pleotropic hyperproducers and pleiotropic hypoproducers of these extracellular enzymatic activities, genotypically designated sacUh and sacU− respectively, have been isolated. sacUh mutants are capable of sporulation in rich media or in mineral media containing amino acids in the presence of an excess of glucose in both cases; under these conditions the sporulation of the wild type strain 168 is inhibited. One pleiotropic mutation conferring hyperproduction of levansucrase and proteolytic activities was mapped at the sacQ locus distant from sacU.

In Bacillus subtilis Marburg 168 an endocellular invertase‐like sucrase can be induced by sucrose. Sucrose, glucose and glycerol exert a catabolite repression on sucrase synthesis in both the inducible strain 168 and a constitutive derivative isolated in this laboratory. Derepressed cultures of this constitutive mutant grown on glutamate and succinate procedure high levels of sucrase and are utilized as starting material for the purification process.The purified preparation gives one single protein band after disc electrophoresis on polyacrylamide gel in the absence or in the presence of dodecylsulphate. This enzyme has a molecular weight of about 55000.Sucrase is not a glycoprotein, it is activated by potassium ions and inhibited by p‐hydroxymercuribenzoate. Arguments are presented in favour of the hypothesis that, in vivo, 6G‐phosphorylsucrose (6‐O‐phosphoryl‐α‐D‐glucopyranosyl‐1,2‐β‐d‐fructof uranoside) rather sucrose serves as a substrate for this enzyme.

Die Saccharase-Aktivität, welche von Bacillus subtilis Marburg erzeugt wird, wird von zwei Proteinen, welche durch Chromatographie an Hydroxylapatit getrennt wurden, getragen. Diese Enzyme sind als eine Levan-Sucrase und eine Saccharase gekennzeichnet worden ; es sind Transfruktosidasen. Ihre Molekulargewichte sind ähnlich (40.000). Die Enzyme unterscheiden sich durch ihre katalytischen Eigenschaften, ihre Empfindlichkeit dem Trypsin und den Reagentien der SH-Gruppen gegenüber, sowie durch ihre immunologischen Eigenschaften. Sie werden beide durch die Saccharose induziert ; nur die Synthese der Saccharase scheint einem Glukose-Effekt empfindlich zu sein. Die Saccharase ist endozellulär, während die Levan-Sucrase in das Kulturmedium abgesondert wird.