Identification and separation of lysosomal carboxypeptidases

Stephen L Taylor, Al L. Tappel

Research output: Contribution to journalArticle

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Abstract

1. 1. Four distinct carboxypeptidases (EC 3.4.12.-) were shown to exist in rat liver lysosomes: cathepsin A, catheptic carboxypeptidase B, catheptic carboxypeptidase C, and catheptic carboxypeptidase G. These carboxypeptidases were distinguished on the basis of substrate specificity, thiol requirement, and separation by Sephadex G-100 column chromatography. The Km and pH optimum for each carboxypeptidase were determined. 2. 2. From the Sephadex G-100 elution profile, two peaks of cathepsin A activity were found. The major cathepsin A peak, cathepsin A1, was further purified by ion-exchange chromatography on DEAE-cellulose. 3. 3. The highly purified cathepsin A1 fraction hydrolyzed N-benzyloxycarbonyl (Cbz)-Glu-Phe, Cbz-Gly-Phe, and Ac-Phe-Tyr, which suggests that these hydrolytic activities were due to the same enzyme. 4. 4. Catheptic carboxypeptidase B and catheptic carboxypeptidase G eluted from the Sephadex G-100 column along with cathepsin B2. This suggests that cathepsin B2 may have carboxypeptidase activity. 5. 5. The purification of the lysosomal carboxypeptidases over homogenate activities was: cathepsin A1, 1280-fold; catheptic carboxypeptidase B, 220-fold; and catheptic carboxypeptidase G, 920-fold. Catheptic carboxypeptidase C was purified 16-fold over light-mitochondrial supernatant activity.

Original languageEnglish (US)
Pages (from-to)99-111
Number of pages13
JournalBBA - Enzymology
Volume341
Issue number1
DOIs
StatePublished - Mar 21 1974

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Cathepsin A
Carboxypeptidases
Cathepsins
gamma-Glutamyl Hydrolase
Carboxypeptidase B
DEAE-Cellulose
Ion Exchange Chromatography
Substrate Specificity
Lysosomes
Sulfhydryl Compounds
Chromatography
Light
Liver
Enzymes
sephadex

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Identification and separation of lysosomal carboxypeptidases. / Taylor, Stephen L; Tappel, Al L.

In: BBA - Enzymology, Vol. 341, No. 1, 21.03.1974, p. 99-111.

Research output: Contribution to journalArticle

Taylor, Stephen L ; Tappel, Al L. / Identification and separation of lysosomal carboxypeptidases. In: BBA - Enzymology. 1974 ; Vol. 341, No. 1. pp. 99-111.
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