PFKL and systemic sclerosis: Assessment of the expression levels of key, rate-limiting enzymes of the glycolytic pathway and lactate secretion on western blots showed that levels of the phosphofructokinase 1 isoform PFKM were significantly lower in SSc fibroblasts compared to control fibroblasts, while levels of the isoforms PFKL and PFKP were unaffected.