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SYNAPTOSOMAL PHOSPHORYLATION OF D‐GLUCOSAMINE

1978; Wiley; Volume: 31; Issue: 2 Linguagem: Inglês

10.1111/j.1471-4159.1978.tb02664.x

1471-4159

C.H. Tan, E. Raghupathy, N. A. Peterson,

Biochemical Analysis and Sensing Techniques

Abstract— Synaptosomal fractions from rat brains can phosphorylate d ‐glucosamine once it is transported across the synaptosomal membrane. Intrasynaptosomal phosphorylation of d ‐glucosamine was rapid; up to 80% of the d ‐glucosamine was recovered as the phosphorylated amino sugar during 15 min of incubation with the substrate. Transport of d ‐glucosamine was the rate‐limiting step in the uptake process since in the presence of cytochalasin B, a specific sugar transport inhibitor, the uptake of d ‐glucosamine was inhibited to the same extent as its phosphorylation. The pH optimum for phosphorylation of d ‐glucosamine by lysed synaptosomal preparations was between 7.5 and 9.0. The mean K m and V max values for this phosphorylation were 0.46 DIM and 676 nmol/mg protein per min, respectively. Phosphorylation of d ‐glucosamine was inhibited competitively by d ‐glucose, 2‐deoxy‐ d ‐glucose and N ‐acetyl‐ d ‐glucosamine and uncompetitively by d ‐glucose‐6‐phosphate. The phosphorylation was strongly inhibited by several sulfhydryl reagents, but was insensitive to product inhibition, cytochalasin B, phloretin and phloridzin.