It is possible to use pumpkin as a substitute for persimmon, although the final result may be different than if you had used persimmon. Pumpkin has a thinner texture and less sweetness, so it may not provide the same flavor or texture that you would get from using persimmon. You can adjust the recipe by adding more sugar or other sweeteners to compensate for the loss of sweetness when substituting pumpkin in place of persimmon. Additionally, because pumpkin is much softer than persimmon, you may need to reduce any cooking time called for in the recipe in order to prevent overcooking. It may also be necessary to add extra binding ingredients such as flour or cornstarch to help hold everything together better since a pumpkin is more watery than a persimmon. Ultimately, it is possible to use pumpkin as a substitute for persimmon in recipes, although you may need to make some adjustments.