Another option is sgolayfilt(). It's like movmean() but instead of fitting a line to the moving window you can fit a quadratic. That should help it follow the big peak better an not smooth it out so much. I'd use a frame (window) length that's large and an order of 2 or 3. Experiment around to get what you like.
plot(x, y, 'k-');
smoothY = sgolayfilt(y, 11, 2);
hold on;
plot(x, smoothY, 'r-', 'LineWidth', 3);
