Purification and partial characterization of three isoforms of serine hydroxymethyltransferase from Crithidia fasciculata

Three molecular forms of serine hydroxymethyltransferase (SHMT) have been detected in choanomastigotes of Crithidia fasciculata by DEAE-cellulose chromatography. The three isoforms (named SHMT I, II, and III) presented small differences in charge and molecular weight. Digitonin treatment of intact c...

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Bibliographic Details
Published in:Molecular and biochemical parasitology 1999-01, Vol.98 (2), p.187-201
Main Authors: Capelluto, Daniel G.S., Hellman, Ulf, Cazzulo, Juan J., Cannata, Joaquı́n J.B.
Format: Article
Language:English
Subjects:
Animals
Cell Compartmentation
chemical structure
Crithidia fasciculata
Crithidia fasciculata - enzymology
Cytosol - enzymology
enzyme activity
Glycine Hydroxymethyltransferase - chemistry
Glycine Hydroxymethyltransferase - isolation & purification
Glycine Hydroxymethyltransferase - metabolism
Isoenzymes - chemistry
Isoenzymes - isolation & purification
Isoenzymes - metabolism
Kinetics
localization
Mitochondria - enzymology
Molecular forms
Molecular Weight
Organelles - enzymology
physicochemical properties
Purification
pyridoxal phosphate
Pyridoxal Phosphate - metabolism
Pyridoxal-5′-phosphate
Serine hydroxymethyltransferase
Subcellular Fractions - enzymology
Substrate Specificity
transferases
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Summary:Three molecular forms of serine hydroxymethyltransferase (SHMT) have been detected in choanomastigotes of Crithidia fasciculata by DEAE-cellulose chromatography. The three isoforms (named SHMT I, II, and III) presented small differences in charge and molecular weight. Digitonin treatment of intact cells suggested that SHMT III is cytosolic, whereas the other two isoforms are particle bound, one being mitochondrial (SHMT I) and the other one very likely glycosomal (SHMT II). The three SHMT isoforms were purified to homogeneity, and their physicochemical and kinetic properties studied. Determination of their native and subunit molecular masses revealed that all of them have a tetrameric structure. The three isoforms were shown to be PLP-dependent enzymes after l-cysteine and hydroxylamine hydrochloride treatments. They showed similar pH optima, bimodal kinetics for l-serine and Michaelis–Menten kinetics for THF.
ISSN:0166-6851
1872-9428
DOI:10.1016/S0166-6851(98)00166-2