Two methods
Set FontSize property
figure()
ax = gca();
set(ax, 'TickLabelInterpreter', 'latex', 'YTickLabel','$\frac{a}{b}$')
ax.YAxis.FontSize = 16;
ylabel('Default label size','FontSize', ax.FontSize)
xlabel('Default label size')
Set FontSize in Latex command
To preserve normalized FontUnit behavior, you can set the fontsize directy in the Latex command. Now, when you change the figure size the title, axis labels, and ticks will resize. However, the ticks may not adjust as they would when you set the axis fontsize property.
figure()
ax = gca();
set(ax, 'TickLabelInterpreter', 'latex', 'YTickLabel', '\fontsize{16}{0}$\frac{a}{b}$')
title('title')
ylabel('xlabel')
xlabel('ylabel')
ax.FontUnits='normalized';
