Prenylcysteine carboxymethyltransferase type III activity is decreased in retinoic acid-treated SH-SY5Y neuroblastoma cells.

Prenylcysteine carboxymethyltransferase (pcCMT) is an enzyme that catalyzes the post-translational carboxymethylation of isoprenylated proteins ensuring a more efficient membrane attachment and proper guiding to a specific target membrane. In this paper, we report on modulation of pcCMT activity in retinoic acid (RA)-treated SH-SY5Y neuroblastoma cells using N-acetyl-S-farnesyl-L-cysteine (AFC) as artificial methyl acceptor. In addition, the methylation of endogenous proteins was followed by the vapor phase equilibrium assay and the storage phosphor screen (P-screen) technique with S-adenosyl-[3H-methyl] methionine (AdoMet) as methyl donor.

Long-term pharmacologic doses of vitamin E only moderately affect the erythrocytes of patients with type 1 diabetes mellitus.

In erythrocytes from diabetic patients, increased membrane lipid peroxidation might lead to abnormalities in composition and function. To study this relationship, we investigated the effects of a moderate pharmacologic dose of vitamin E for 1 y on erythrocyte membrane peroxidation in vitro and on its fatty acid composition, antioxidant capacity and rheological function. In a random and double-blind manner, type 1 diabetic patients (n = 44) were assigned to the following two groups: Group S received 250 IU (168 mg) d-alpha tocopherol 3 times daily for 1 y.

On the occurrence of multiple isoprenylated cysteine methyl ester hydrolase activities in bovine adrenal medulla.

Rab proteins intervene in the controlled exocytosis of catecholamines by chromaffin cells from the adrenal medulla. These proteins are posttranslationally modified by digeranylgeranylation and carboxymethylation. Reversible carboxymethylation terminating the isoprenylation pathway may play an important role in both the functioning and the subcellular housing of small G-proteins.

Identification of prenylcysteine carboxymethyltransferase in bovine adrenal chromaffin cells.

Chromaffin cells from bovine adrenal medulla were examined for the presence of a specific prenylcysteine carboxymethyltransferase by using N-acetyl-S-farnesyl-L-cysteine and N-acetyl-S-geranylgeranyl-L-cysteine as artificial substrates and a crude cell homogenate as the enzyme source. From Michaelis-Menten kinetics the following constants were calculated: K(m) 90 microM and V(max) 3 pmol/min per mg proteins for N-acetyl-S-farnesyl-L-cysteine; K(m) 52 microM and V(max) 3 pmol/min per mg proteins for N-acetyl-S-geranylgeranyl-L-cysteine. Both substrates were methylated to an optimal extent at the pH range 7.