Douglas E. Hall

Hydroxyproline metabolism by the rat kidney: distribution of renal enzymes of hydroxyproline catabolism and renal conversion of hydroxyproline to glycine and serine.

The metabolism of hydroxyproline by the rat kidney leads to the production of significant quantities of both glycine and serine. This process was observed in both the isolated perfused kidney and in isolated cortical tubule suspensions. The rate of hydroxyproline metabolism was increased in both preparations by the addition of alanine. The distribution of hydroxyproline oxidase, hydroxyoxoglutarate aldolase and alanine-glyoxalate transaminase were determined in detail. All three enzymes were found exclusively in the renal cortex where they were restricted to the mitochondria. Cortical tubule fractionation studies indicated that the enzymes are located in the proximal convoluted and proximal straight segments at the nephron. The results suggest that hydroxyproline degradation could contribute significantly to the renal synthesis of serine.

Insensitivity of the amino acids of canola and rapeseed to methanol-ammonia extraction and commercial processing

Abstract Amino acid composition of rapeseed meals treated with ammonia in absolute or 95% methanol was compared to those of their hexane-extracted counterparts as well as a commercially processed meal. Meals of Altex canola, Midas rapeseed, and Hu You 9 Chinese rapeseed were used. Few differences were found in the essential amino acid contents due to these treatments. Partial extraction of non-protein nitrogen compounds may be responsible for the observed differences. Protein efficiency ratio (PER) values of meals, calculated on the basis of the content of selected amino acids, varied from 1.7 to 2.4, depending on the seed variety. The processing conditions did not affect the calculated PER values to any great extent.

Hyalin, a sea urchin extraembryonic matrix protein: Relationship between calcium binding and hyalin gelation

The protein hyalin, a major component of the sea urchin extraembryonic hyaline layer, was previously shown to undergo a Ca(2+)-induced self-association into large aggregates (gelation). This reaction represented a major step in assembly of the layer. In the experiments reported here, digestion with trypsin resulted in a rapid dissociation of hyalin into a mixture of peptides which retained the capacity to bind Ca2+. However, unlike intact hyalin, none of these peptides associated into large aggregates (gelation) in the presence of Ca2+, Mg2+, and NaCl. Loss of the ability to undergo gelation was not accompanied by any significant change in the content of acidic plus amide amino acid residues. Decreasing the pH to 5.6 resulted in a loss of 25% of hyalins Ca(2+)-binding capacity but had no effect on the ability of the protein to undergo gelation. Peptide fragments were only partially effective at inhibiting hyalin gelation. Clearly, not all the Ca(2+)-binding sites were required for hyalin gelation and Ca2+ binding alone was insufficient to drive this reaction. In addition, hyalin appeared to possess two classes of protein-protein interaction domains, one of which was essential for gelation.