Panneerselvam K, Balasubramanian A S
Neurochemistry Laboratory, Christian Medical College Hospital, Vellore, India.
Neurosci Lett. 1991 Oct 28;132(1):26-8. doi: 10.1016/0304-3940(91)90424-r.
alpha-D-Mannosidase that exhibits a pH optimum close to neutrality (neutral mannosidase) purified from monkey brain cytosol is known to be stimulated by Co2+ and this stimulation is suggested to be mediated through a Co2+ activated aminopeptidase that is inseparable from the neutral mannosidase and that cleaves amino acids from the neutral mannosidase. In the present studies, the phosphorylation on serine residues of the neutral mannosidase by cyclic AMP dependent protein kinase is demonstrated. After phosphorylation the mannosidase activity remained unchanged, but it was not stimulated by Co2+. The aminopeptidase activity, although it retained its response to stimulation by Co2+, showed a drastic reduction in its activity after phosphorylation. It is suggested that the loss of Co2+ sensitivity of the neutral mannosidase after phosphorylation is mediated through the aminopeptidase.
从猴脑细胞质中纯化出的α-D-甘露糖苷酶，其最适pH接近中性（中性甘露糖苷酶），已知该酶受Co2+刺激，且这种刺激被认为是通过一种与中性甘露糖苷酶不可分离的Co2+激活的氨肽酶介导的，该氨肽酶可从中性甘露糖苷酶上切割氨基酸。在本研究中，证实了环磷酸腺苷依赖性蛋白激酶对中性甘露糖苷酶丝氨酸残基的磷酸化作用。磷酸化后，甘露糖苷酶活性保持不变，但不受Co2+刺激。氨肽酶活性虽然仍保留对Co2+刺激的反应，但磷酸化后其活性急剧降低。有人认为，磷酸化后中性甘露糖苷酶对Co2+敏感性的丧失是通过氨肽酶介导的。
