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C F Heredia

Publications and source records attributed to C F Heredia.

28 records · Page 2Linked to original sources
PubMed1978

N-acetylphenylalanyl-tRNA hydrolase from yeast. Purification and properties.

This paper describes the purification and properties of an enzyme present in yeast which splits N-acetylphenylalanyl-tRNA to N-acetylphenylalanine and tRNA. The enzyme has been 35000 as estimated by filtration on Sephadex G-150, is maximally active in the presence of a divalent cation (Mg2+ , Mn2+ or Ca2+) and has a pH optimum at around neutrality. The enzyme is highly specific in hydrolyzing N-acetylphenylalanyl-tRNA (Km = 0.4 micron). Phenylalanyl-tRNA is hydrolyzed with a similar apparent affinity but with an efficiency of 40% of that found for N-acetylphenylalanyl-tRNA. Other free or N-substituted aminoacyl-tRNAs are not substrates of this hydrolase. Neither of the two reaction products are effective inhibitors of this enzyme. Based on its substrate specificity, the trivial name of N-acetylphenylalanyl-tRNA hydrolase is proposed for this enzyme.

Carboxylic Ester Hydrolases↗
PubMedDate not supplied

Characteristics of the inhibition and metabolic inactivation of the yeast TRNA nucleotidyl transferase.

1. Yeast tRNA nucleotidyl transferase is inhibited by low molecular weight compounds present in cell-free extracts. The inhibition produced by the main component(s) is competitive with respect to ATP and is not prevented by metal chelating agents. The major component(s) has been partially purified. It is resistant to heat (90 degrees C, 5 min) and insensitive to digestion by alkaline phosphatase, snake venom phosphodiesterase and inorganic pyrophosphatase, indicating that it is not a nucleotide. 2. Besides the masking of the transferase activity in the crude extracts by the inhibitors, the enzyme is inactivated in nitrogen starved cells. The inactivation also occurs in yeast mutants lacking several proteases and is not prevented by inhibitors of yeast proteases. These results rule out extracellular proteolysis as the cause of inactivation and strength our previous observations on the metabolic inactivation of the transferase in response to nitrogen starvation.

Adenosine Triphosphate↗