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

An endonuclease from yeast mitochondrial fractions

A membrane-bound endonuclease has been isolated from mitochondrial fractions of Saccharomyces cerevisiae. The enzyme is present in a stable complex and has an approximate molecular weight of 14 000. It requires Mg2+ or Mn2+ for activity, and has an optimum pH of 7.0. Its activity with native DNA is five times less than with denatured DNA in 0.05 M KCl and is very low in 0.2 M KCl. The activity with RNA is 40% of that with denatured DNA; the two substrates are competitive. Its mode of action is endonucleolitic, cuts both strands of native lambda DNA at the same or nearby sites. After mild digestion of DNA, analysis of 5'-end groups of the digestion products indicated a marked preference for deoxythymidylic and deoxyguanilic acid residues as the site of enzymatic cleavage. After exhaustive digestion of DNA, mononucleotides (2.4%), dinucleotides (70.5%) and trinucleotides (27%) ending in 5'-phosphate are produced.

Quantitative data on the Bombyx mori L. silkworm: a review

This paper summarizes a variety of quantitative data on the silkworm Bombyx mori, collected in the literature, to help building models on silk gland differentiation. The properites of the silk gland and their changes especially during the last larval instar have been reviewed (size, DNA, RNA amino acids, enzymes). The components of the silk (fibroin and sericin) are also studied (molecular weight, composition). Thus translation and transcription rates have been estimated. The relevant data on the fat body and the haemolymph are also given, as well as some characteristics of the oocyte/egg system.