guanosine + phosphate <=> alpha-D-ribose 1-phosphate + guanine
guanosine + phosphate <=> alpha-d-ribose 1-phosphate + guanine
guanosine + phosphate <=> alpha-D-ribose 1-phosphate + guanine
guanosine + phosphate <=> alpha-d-ribose 1-phosphate + guanine