Variants of a Pseudomonas saccharophila G4-forming amylase (PS4) advantageously can catalyze high temperature saccharification to produce maltotetraose syrup from a starch liquefact or granular starch, e.g., derived from cornstarch. The PS4 variants are useful in a process of saccharification of starch that advantageously produces significant amounts of maltotetraose, which can be used downstream in a process of producing a maltotetraose syrup. In one embodiment, a thermostable PS4 variant is provided that can produce about 40% to about 60% by weight maltotetraose, based on total saccharide content.