Putting in chronological order the following steps involved in glycogen synthesis from galactose, which step is the fourth (second-to-last) step in the process?
Imagine a cell with three excess galactose molecules that must be converted to glycogen for storage. This cell has developed a mutation in galactokinase that allows the enzyme to use GTP as a phosphate donor rather than ATP. In this scenario, how many inorganic phosphate molecules (Pi) would be generated following the polymerization of the three galactose molecules into glycogen?
Under normal conditions, the galactose 1-phosphate uridyl transferase (GALT) enzyme shows 1000-fold higher activity toward galactose 1-phosphate than does the UDP-glucose pyrophosphorylase enzyme (UDP-glcPP). However, some individuals lack functional GALT enzyme. In such cases, UDP-glcPP enzyme begins to use galactose 1-phosphate as a substrate instead of glucose 1-phosphate. Under these unique circumstances, which of the following enzymes normally involved in galactose-to-glycogen metabolism becomes unnecessary?
