Inactive atromentin synthetase homolog. While the invA3 adenylation (A) domain is capable of adenylating 4-hydroxyphenylpyruvate (4-HPP), the invA3 enzyme is inactive because of its non-functional thioesterase (TE) domain. Optimum pH is 6.8. Optimum temperature is 20 degrees Celsius. Belongs to the ATP-dependent AMP-binding enzyme family.