TY - JOUR
T1 - Effect of methionine, glycine and serine on serine hydroxymethyltransferase activity in rat glioma and human neuroblastoma cells
AU - Kohl, Randall Lee
AU - Perez‐Polo, J. R.
AU - Quay, W. B.
PY - 1980
Y1 - 1980
N2 - Human neuroblastoma SK-N-SH-SY5Y (5Y) and rat glioma (C6) cells were cultured with supplemental methionine, glycine, or serine for 3 to 6 days. Serine hydroxymethyltransferase (SHMT: L-serine: tetrahydrofolate 5,10-hydroxymethyltransferase, EC 2.12.1) was assayed radiometrically in whole cell homogenates, crude supernatant fractions and crude particulate fractions. No significant changes in specific activity or cellular morphology were noted at methionine, glycine, or serine concentrations up to 16 mM. Serine concentrations of 20 and 40 mM led to significantly lower gliomal enzyme specific activities. This activity was unevenly distributed between soluble and particulate fractions, with 190 and 398 nmoles of HCHO formed per mg of protein per hour, respectively. Growth stage and time of incubation were major determinants of enzyme specific activity. C6 cells' specific activity rose slowly with increasing time in culture until cellular confluence. At this time there was a pronounced elevation in specific activity, occurring more rapidly in cells grown in 1.2 mM methionine. Intracellular amino acid analysis of C6 cells demonstrated a significant rise in methionine after 4 days in media containing 0.2 mM methionine. No appreciable diminution in the intracellular levels of glycine or serine occurred following incubation in excess methionine. It is concluded that SHMT-specific activity in C6 and 5Y cells is not regulated by glycine, serine, or methionine levels and that high concentrations of these amino acids (> 30 mM) are not detrimental to these cells derived from the CNS.
AB - Human neuroblastoma SK-N-SH-SY5Y (5Y) and rat glioma (C6) cells were cultured with supplemental methionine, glycine, or serine for 3 to 6 days. Serine hydroxymethyltransferase (SHMT: L-serine: tetrahydrofolate 5,10-hydroxymethyltransferase, EC 2.12.1) was assayed radiometrically in whole cell homogenates, crude supernatant fractions and crude particulate fractions. No significant changes in specific activity or cellular morphology were noted at methionine, glycine, or serine concentrations up to 16 mM. Serine concentrations of 20 and 40 mM led to significantly lower gliomal enzyme specific activities. This activity was unevenly distributed between soluble and particulate fractions, with 190 and 398 nmoles of HCHO formed per mg of protein per hour, respectively. Growth stage and time of incubation were major determinants of enzyme specific activity. C6 cells' specific activity rose slowly with increasing time in culture until cellular confluence. At this time there was a pronounced elevation in specific activity, occurring more rapidly in cells grown in 1.2 mM methionine. Intracellular amino acid analysis of C6 cells demonstrated a significant rise in methionine after 4 days in media containing 0.2 mM methionine. No appreciable diminution in the intracellular levels of glycine or serine occurred following incubation in excess methionine. It is concluded that SHMT-specific activity in C6 and 5Y cells is not regulated by glycine, serine, or methionine levels and that high concentrations of these amino acids (> 30 mM) are not detrimental to these cells derived from the CNS.
KW - enzyme regulation
KW - glycine
KW - methionine
KW - one‐carbon metabolism
KW - serine
KW - serine hydroxymethyltransferase
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U2 - 10.1002/jnr.490050403
DO - 10.1002/jnr.490050403
M3 - Article
C2 - 6776288
AN - SCOPUS:0018970361
SN - 0360-4012
VL - 5
SP - 271
EP - 280
JO - Journal of Neuroscience Research
JF - Journal of Neuroscience Research
IS - 4
ER -