The isoinhibitors of chymotrypsin/elastase from Ascaris lumbricoides: the primary structure.

The complete primary structure of five chymotrypsin/elastase isoinhibitors isolated from Ascaris lumbricoides was determined by conventional methods. These structures represent the first sequence set for the Ascaris inhibitor family. All five isoinhibitors are single-chain polypeptides crosslinked by five disulfide bridges. Isoinhibitor 1 consists of 63 amino acid residues and has glycine at the N-terminal and histidine at the C-terminal. Isoinhibitors 2-5 all have arginine at the N-terminal, differ at positions 25 and 40, and have different C-terminal regions. Isoinhibitors 2 and 4 have asparagine at positions 25 and serine at position 40, whereas isoinhibitors 3 and 5 have lysine and threonine at these positions, respectively. The different C-terminal regions of isoinhibitors 2-5 account for their varying lengths. Isoinhibitor 1 has no sequence heterogeneity. Frequent repetitions of various dipeptides and one tripeptide are evident along the peptide chain of isoinhibitors 2-5. None of the isoinhibitors contains the aromatic amino acids phenylalanine or tyrosine. Comparison of the amino acid sequence of isoinhibitor 1 with the sequence of isoinhibitors 2-5 shows that they differ at a minimum of 16 positions. The primary structures of isoinhibitors 1-5 from Ascaris do not demonstrate a great degree of homology when compared with the sequence of presently known proteinase inhibitors. However, these isoinhibitors share with a very large number of inhibitor families the presence of half-cystine in the P3 position.

Selenium nutriture in total parenteral nutrition: intake levels.

More attention is being given to the essential trace elements in human nutrition, although there is much to be learned concerning requirements, function, and interactions. The extensive use of total parenteral nutrition (TPN) provides an opportunity for further study. To date, little attention has been paid to selenium (Se), an element for which both a deficiency and toxic state can exist. In a program to evaluate the effects of long-term TPN on Se nutriture, a avriety of solutions used in TPN have been analyzed. Se was not present in detectable levels in the following solutions: sodium acetate, Freamine II, NaCl, potassium phosphate, KCl, Folvite, Liquaemin Na, CaCl2, MgSO4, and NaHCO3. The solutions containing significant amounts of Se were: 50% dextrose 0.27 +/- 0.04 microgram/ml and 20% dextrose 0.27 +/- 0.08 microgram/ml (Travenol Laboratories); 50% dextrose 0.47 +/- 0.10 microgram/ml and 20% dextrose 0.35 +/- 0.07 microgram/ml (Abbott Laboratories); and 70% dextrose 0.33 +/- 0.08 microgram/ml (McGaw Laboratories). These data suggest that 200 to 400 microgram Se would be provided in the usual amounts of solution administered to an adult patient.